Hey man, thanks for the insight!
Well, I should probably have chosen my words better. The "problem" with the MSR7 is that, while it's crystal clear at lower volumes (highs are perfect until a certain point on the volume pot), if I push the volume to gain more oomph it starts to get a bit noisy in the treble/high mids. It's not distortion that I'm hearing, I'm quite sure it's reflections from inside the cup or something like that (I get the same thing on my HD58x if I push the volume and put my palms on the back of the headphones, albeit to a lesser extent). That's what I'm after, not tuning the FR. That I know how to do, and it's going to be my solution if I can't solve this the way I think I want to do it. I don't even know if I'm making any sense at this point.
If it comes down to any manner of dampening to tune the FR to be more high volume friendly, I'm covered.
@ModiHiFi over at the MSR7 owners' thread has done an excellent job of testing different materials both in the front and the back of the driver, much more than I've been able to do.
So, it seems that if I can find some dynamat on the cheaper end locally, I could give it a try, but not expecting wonders, got that. Thanks for probably saving me like 40€.
Anyone here use bluetack or something like it in a similar manner?