For me personally, I'm willing to trade some tonality for comfort.
I've had this thought in my head... but have never been willing to go through with it: cut out the inner ring of leather/pleather from the pads, so that the foam is exposed. I have a feeling this would greatly increase absorption and strongly cut down that ear chambering treble
A long time ago I had this beat up pair of Sony V6's where the pads were so worn the stitching on the inside was gone and it was just exposed foam. Not only did I find them more comfortable, but the sound was also much more pleasing to my ear. Now whether or not that was a comfort/psychoacoustic thing, I can't say for certain.
See, to my head the J$beyers and regular pleathers are a tradeoff in terms of comfort, J$'s have better softer material and larger surface area and so it is nicer-feeling, but pleathers are only about half the thickness so it is only half the clamping force.
I don't know about cutting an entire inner ring of the underside out, there is some pressure retaining the foam inside the pads, if you cut an entire ring out there's a fairly good chance that over some use a lot of the foam would protrude out of the cut openings.
I just finished doing this, haven't listened yet but I thought I'd share what I did with the retention ring. Instead of completely removing the vinyl ring that holds the plastic clip to the earpad, I cut it open so it only has 5 small attached points to the pleather on the earcup. This allows me to continue to use the standard retention system without tape or glue and still be open, hopefully as good as complete removal.
Cool idea retaining the flaps. Not the cleanest cutting job but it should have the same mod effect.
So, I was kind of thinking about regaining some warmth and bass.
Considering, damping largely makes the difference between velours and pleathers, I decided to cut the eight most centric holes larger.
Result with HE-500: So, you lose a bit of air and stage and gain a slightly darker sound, which then also sounds a bit warmer plus you gain a bit of bass punch. Obviously, I cannot do an A/B ;) but I think this inner damping is quite influencing the tonal balance. For me the some of the velour sound was added now and the tonal balance is more even between treble and bass. I will A/B it more detailed with with velours some time soon.
This might be it now :)
I'm beginning to think that the critical part of the mod is the inner-most circle of damping rings too. Will likely try it sometime as well, and if the effect is immediate and positive, revise the original guide.