I just removed the cloth on the grill, didn't touch the felt. Shelf liner behind the ear pads, and I am using Focus Pads with the foam ring from the stock HE-6 pad, inside the Focus Pads, a tight fit but it works for a more spacious ear pad. The foam ring helps the seal for better bass, no paste/putty/eraser.
I also said this was on my setup, and I use a Norne Draug 2 cable.
Right on, maybe when all is said and done I might go back to the HE4 and mod it as well. At this point I don't see it happening anytime soon but the modding seems to promise great results on it.
Also, I just ordered some Aluminum baffles for my HE560. The head-room site was a bit unclear wether or not 1 order comes with a pair or a single so I ordered a qty of 2. If it is for a pair, I'll be having an extra set for sale for $13 shipped. This should make the connection between driver/baffle/pad even tighter creating better control on the bass and overall sound/clarity. At least in theory, not sure how well it'll work for the HE4 but if anyone is interested if I end up with an extra set, I'd love to hear how it does for the the HE4.