Done. Wow. The refined highs from the stock pads are back. Not as dull and dark as my second experience, which was a bit of cloth, yet no sibilance of unmodded oval pads. I don't have a lot of experience with quality gear and the best source I've ever had is a humble Cowon D2+ (rockboxed and patched for added voltage) so I wasn't sure I'd be able to hear the difference, but now it's obvious that the worst thing about sibilance (for me) is not even the harshness but a lack of timbre. The highs just didn't sound like real thing before your mod. So yeah, thanks a ton!
It's actually quite common, the paper mod. The sennheiser HD-25 1 II comes with paper in front of the driver right from the factory. Or atleast something that looks very similar to paper!