this thing is huge im trying to fit a 12x12x12 sub box but itwont go in...do you guys know if it can be cut through the center and still be held up? or can it all come down

 

if you cut a big enough hole, and use enough duct tape they you can absolutly beat that square peg(litteraly!) into that round hole and then patch it up with the duct tape.

IT would be a better idea to get a box that will fit the vehicle then it will to try and ruin your mustang to make the vehicle fit the box.

 

I don't know how you can't get that in. That is 1 cu ft. I have fit a 4.5 cube in my mustang...