Tried using electrical tape over one section of the driver "grid". With that, 6 cotton balls per cup, vents left open (with stock felt in place), Silverstone foam on ear side baffle and lining cups, Plasticine in the back of the driver baffles, and the 840 pads, these are actually sounding pretty great. I just wish they had more sub-bass. They certainly extend deep, but the bass rolls off earlier than I'd like.
I'm also having an issue where the right driver will buzz/sound distorted in specific parts of some songs. I don't get this with other headphones...