is it possible to build boxes that would install in place of the factory rear side panels? I'm looking to put in 4 10"ers one in front of wheel well & one behind. I'm not worried about not being able to get to the last hardtop bolt (the one that bolts in from bottom at back) 'cause I never put it back in anyway. If so, could anyone give me some specs on box dimensions? I know just enough to know that I'll never know enough.