Well, my love affair with my modded YH-3s turned out to be a one night stand. Her older, longer legged, bustier sister showed up and took off the baggy sweat suit to show off her curves! DAMN!

I took what I learned from the YH-3s and applied it to rythmndevils YH-100s. Now I'm in love with another man's girl! LOL!
Bass is better, deeper, tighter, cleaner... Highs smoother and the headstage is at least 3 times wider than my YH-3s. Still not quite K601 open, but they don't feel congested or closed. The highs are almost piercing with ESW9 pads as the larger ID really let's the Yammy mids sing through, but awesome with certain music. The R10 pads are great for a wider range of music, though a touch darker with much deeper bass than the ESW9 pads. I'd probably swap pads back and forth, depending on my mood and desired music. Example, female singers and acoustic I'd use ESW9s and sacrifice the elevated bass output, but rock and hip hop really need the R10 pads for the bass and to take off the highs a bit as synthesized high hurt like hell with the ESW9 pads. Just too forward and strong. For my tastes anyways. I know a certain H-F'er in Greece that would love the sound of the ESW9 pads all the time.
I'll say I have the YH-100s 99.5% of what I feel I'm personally capable of getting out of them. Last tweak I'm going to try tonight is to stretch the R10 earpad ID a bit to open it up more for better treble extension like the ESW9 pads. BUT, that means I have to take them off and go to bed.
The best part? The mid-bass honk at higher volumes is gone. Now the mid bass still gets a
little louder with the R10 pads, but only
slightly and it doesn't muck up the mids. With the ESW9 pads, the mid bass is reduced enough that the mids lead when really cranked up. Really neat effect to hear, it doesn't sound like EQ, it just steps forward a bit.
Oh, I guess you want to know what I changed...
Kept the 30mm diameter surgical tape disc on the center, added tape to cover three (or four - I forget) more holes on each side, leaving the three holes at each corner open. Then a full disc of the Moorbrook felt over the back, held in place only by a dot of blu-tak the size of the center rivet. My 42mm-45mm fiberglass "egg yolk" in the center of the cup with the cotton in the back center pivot. A ring of blu-tak around that raised ridge at the back. The black perf'ed synthetic felt in the vents. Then I added the "egg whites" in the form of an unrolled cotton ball that I rolled and mildly felted like a snake and wrapped it around the FG yolk. Then I put blu-tak on the inside edge of my pad adapters to make sure there was no leaks in the adapter to front bezel interface.
I think rythmndevils will be happy with the sound, especially if I can squeeze just an once more juice out of the treble with the ID stretch...
BAD NEWS ALERT!
No pics... yet.