they pull right off.. just stick your thumb under the padding...between the pleather and the cloth part that is against the driver cover...push out towards the edges and the cover should come off the edge
try comparing it to an unmodded one... the difference is quite large. so large infact that i didnt like the highs boosted that much. so i literally put a sock in it. i cut out a layer of an old sock and put it between the driver and the stickytac to tone down the high frequencies.
well i think the purpose of this puddy is to tone down the resonance thats going on inside the headphone behind the driver so yes the amout of air in it and the shape should make a difference, as it does in any kind of enclosure