I agree, I cut my 92 chevrolet silverado extended cab, to put in two audiobahn 1805's and two mmats d300hc's. I noticed a lot more flex in the cab, namely the back window. I ended up welding in re-enforcements and it helped alot. But my subs always got dirty in the bed, I tried to seal it, but its **** near impossible. I never went off roading but I could only imagine my truck falling apart if I would have. I used an acordian style weather boot to seal the opening and plenty of window silicon. I tried facing the subs in the truck, then I rebuilt my box with subs facing bed and the ports coming out the back of the box into the cab. It was sealed around the box so that only the ports fired into the truck and it was incredibly loud inside the truck and outside, It flexed my back window and fiberglass bed cover a lot. It was a pain in the *** to do it though and I would not recommend it(especially if you are not quite educated because you could cut through structural supports). However i was the only one around that I had seen with it done. Whatever you decide, good luck.