[grunge311]

The headroom would not change at all, since your not lifting the seat actually, just changing the angle at which your legs rest. to allow a larger opening for the sub in the front. It should work out great for fitting a 10" sub

I was just thinking that in the back of my KC its already so uncomfortable, the angle of the back of the seat in relation to the seat, that to alter that angle would make them even more uncomfortable.

I would be more inclined to removing the 40% seat and building something there that housed 2 12s, and a flat top to set stuff on etc, maybe some compartments to put stuff, etc, since I am so tall noone can sit behind me that seat is wasted anyway, might as well remove the seat all togeter, build the sub box you really want to build, and have some extra storage space.

Your sub box project sounds cool though, post pics when you are done.