Here is to be collected links to the most instructive posts on how to modify the Fostex T50RP, mostly from this thread: Just listened to some Fostex T50RPs today... WOW!
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow
This is not for "Thunderpants" - only modifications keeping the standard cups
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BMF:
BMF is bluemonkeyflyers mods.
BMF 6.3
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4290#post_7856037
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4440#post_7865771
BMF 6.1 vs 6.2
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4155#post_7840197
BMF 6.2
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4125#post_7837614
BMF 6
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/3945#post_7827522
BMF 5
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/3840#post_7823213
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/2640#post_7768186
BF Transpore mod
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4875#post_7900702
bluemonkeyflyer's modified rastapants with picture walk through
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/2655#post_7768646
more from bluemonkeyflyer
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4620#post_7877085
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4560#post_7872751
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4365#post_7861181
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4245#post_7851889
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4035#post_7832914 (applying dynamat)
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/3045#post_7790852
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/1785#post_7582437
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/2715#post_7771999
bluemonkeyflyer on temporary closing the cups in between mods:
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5340#post_7949196
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5295#post_7945865
bluemonkeyflyer compares unmodded and modded T50RP to LCD-2 etc.
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/3690#post_7816428
follow up
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/3735#post_7817267
simple mod
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4440#post_7865771
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RASTAPANTS:
Rastapants 2 by mrspeakers:
Rastapants 2 840 Pad Edition:
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4260#post_7852863
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/3525#post_7808672
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/3525#post_7808673
Rastapants 1 by mrspeakers
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/2445#post_7746934
Rastapants by mrspeakers pictures
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/1380#post_7357008
mr speakers measurements
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4200#post_7846094
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4185#post_7845429
mr.speakers sbour RP2 and O2 pads
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/3705#post_7816511
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HDman T50ResPonse
http://www.head-fi.org/t/583371/t50-response
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5220#post_7938002
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5175#post_7932721
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OTHER MODS
mmda - simple glue and clay mod
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/6060#post_8109855
BmWr75 simple mods (a BMF variant)
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5745#post_8037638
LFF "Paradox"
It is a secret.. elaborated here
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5295#post_7947203
hans030390's modded T50RP (Updated 12-15-2011)
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5490#post_7972850
Fat person T50RP by snakeeater69
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4995#post_7911193
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4485#post_7867736
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4470#post_7867493
Very very easy mod with K240 Sextett pads by RexAeterna
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4965#post_7908749
mmayer167 easy mod with O2 pads
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4635#post_7877318
rawster picture walk through RP2
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/3885#post_7824377
SPwild's mod
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/330#post_6998354
Cheap mod by dogears
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/2445#post_7748868
Jonclarke doing tidy work with Paxmate and Dynamat - pics
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/1575#post_7436860
PhaedraCorruption picture tutorial
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4485#post_7867505
ambchang's two mods comparison
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5130#post_7926639
Faust mod:
http://wiki.faust3d.com/wiki/index.php?title=Image:T50RP_m2.jpg
b0wl1ngs variant:
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/1785#post_7583476
SlaRe comments: "Tried this one, seems like the best best if you don't have paxmate. It's impressive what just a thin piece of felt glued over the driver can do, really good isolation too."
Smeggy's old setup:
http://www.head-fi.org/t/111193/orthodynamic-roundup/6555#post_5220171
Rastapants in the flesh:
http://cdn.head-fi.org/a/a3/a33b16c8_2970acf8_rastapants.jpeg
SlaRe comments: "Works best with 840 or O2 pads apparently. The leeperry mod is basically the same thing, only you leave the white felt over the driver."
LFF headband suspension
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/2895#post_7782196
Twinster's sound reflection cardboard cookie
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5490#post_7972312
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GENERAL ARTICLES
How to easily assemble and re-assemble while trying out different mods
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5595#post_7997986
AnotherN00b sum's up modding
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5175#post_7931332
Fostex T50RP Modification: A Summary of Methods, Materials, and Their Possible Effects
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/2640#post_7768186
bluemonkeyflyer - Modding Noob Extraordinaire
Armageis on damping
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/3795#post_7820049
High End Phones-Comparison
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4230#post_7850268
Exploded parts view
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/1845#post_7610095
Tyll Hertsens explains about orthos in general and why they are especially sensitive to good acoustic damping
http://www.innerfidelity.com/content/how-planar-magnetic-headphones-work
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MATERIALS:
Paxmate
Acoustipack
Dynamat
Newplast
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PADS:
Beware that pads have influence on sound, and the mods are adjusted to the pads. Always keep in mind what pads are used by a modder.
Shure HPAEC840 Replacement Ear Cushions For SRH840 Headphones
Shure HPAEC940 Replacement Velour Ear Cushions for SRH940
Beyerdynamics DT990 Velour pads (black or grey)
Fischer FA-003 pads
Audez'e LCD-2 pads
Stax 007 pads http://www.ebay.com/itm/390342410864?ssPageName=STRK:MEWNX:IT&_trksid=p3984.m1439.l2649
Smeggy's description of various pads
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/4485#post_7868175
Useful "Sock Mod"
to avoid those platic earpads making you sweat. I did this - and ignored the cardboard part, just stuffed the cloth under the pads

http://www.head-fi.org/t/470304/shure-srh840-earpad-mod
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HEADBAND:
HD280 pad mod by satwilson
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5505#post_7973404
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/5520#post_7980238
LFF headband mod
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Total makeover mods (new cups)
Thunderpants
KODA^2 / KODA^1
http://www.head-fi.org/t/582736/koda-2-k-nigs-ortho-dynamic-acrylic-headphones#post_7927522
http://www.head-fi.org/t/582736/koda-1-the-ortho-dynamic-prototype-project#post_7927522
Leakypants