So, I got to modding the MSR7 so that they play better with the HM5 pads. And boy, oh boy, did I do just that... Let's start!
First thing you do is take the pads off, and undo the 8 screws underneath. Should be pretty self explanatory. Then you gently take the baffle off
(GENTLY, unless you like soldering) and you can see a small hole covered by a felt in the center.

Then you have to take the middle plate off the cup. To do this, you lift the small piece of tape holding the wire
(don't yank it because it may pull the wires with it, and save it somewhere safe) and then pull
(again, gently, there's more soldered thin wires beneath that) the whole thing while wiggling it a bit. After a while the cup should be seperated from the middle plate. Line up the top baffle that holds the driver with the lower part so that the little wire is straight and pull the midplate upwards so that it goes away from the cup and closer to the baffle. Here you can see the little felt ring from behind.

Remove it gently, so that you don't rip it
(although it does hold itself together well, even though the adhesive is quite strong) and save it somewhere in case you want to revert the whole thing. Then put the whole thing back together. Boom, that's it. No potentially distortion causing materials in front of the drivers, no nothing. Just added bass. I think that there's even more than stock, even when using the HM5 pads. I also think it sounds a bit more open and leaks a bit more sound, but that could be the pads, so I digress. Now I have to make the pads fit more snuggly in the groove somehow, 'cause they're big and they got stretched when I was using them over the whole cup and now the elastic band is a bit loose. Meh.
@ModiHiFi I think you more than anyone will appreciate this. Just give it a try, you're gonna love the result! Maybe even give it a shot with your own mods with the batting fleece over the driver and see what happens! Down the road I'm gonna experiment with filling the cups with cotton or, if I can find any, polyfill. But as it stands I'm more than happy with the result!