Wouldn't that how a "bass lens" would work essentially, yes? Have you tried using stiff felt instead of a smaller earpad? I've only tried this on my Portapro and my T50RP at one time, using felt and a bit of foam. Punchy bass and quite shrill highs, even with the foam, from memory. And it seems to focus the air into something that punched me straight into my brain and give me headaches though.
But that was before I did my latest 2 mods though (just the all standart newplast-in-baffle, paxmate in cups and cotton.) as at that time I find the bass is a little too few. IMO people should try melamine sponge (magic eraser or something it's called household-commercially). I find it increase bass impact and soundstage quite cleanly and adds a little bit energy in the treble, unlike my experience with cotton.