thats a good idea!

I'm not sure what the area under your front passenger seat looks like, but this is an idea that worked on my old GP. My husband and I bought a little Alpine 6 disc CD changer and put it under the seat, from the back, so the driver can reach back and pop the discs out while driving. Worked great, and we hid the wires under the rug so it looked good too (just watch out for those back seat passengers...I had more than one foot go through the door of the changer :? ).

what about mounting it to the drivers side of the console down by the shifter, where the vynl meets the carpet, sort of by the seat?

You could gut the other storage compartment on the dash and prolly nail a 12er in there I did a lil bit of measuring and it will fir my old sony 6 disc that is about the size of todays 12 disc anyways it looks like of you moded the door and the back of the box I think you should be okay height wise. Maybe this is a better route? might look kewl... Just a thought