yes a big concern, We used bus seats with hip seatbelts, plenty of stuff flew thru the bus. The fridge door that has a lock on it busted open, the rear door got so twisted that that it opened up. This was only a side impact.. the front bumper is hardly bend.. A lot of self tapping screws got just ripped out of the metal because they were designed for shear and suddenly they got exposed to pull forces.
Looking at ethe bolts for the seats... 5 pieces 5/16" with backup plates ..to hold two kids in place.. That does not bode well for a bunch of drywall screws holding 2x4 together.
I left the inner roof panels and with a roll over they are essential in holding the roof up. They are stressed skin and together with many screws or rivets they form a nice box profile. A wood ceiling made of tongue and groove is not the equivalent of a stressed skin.
anyhow with so many skoolies being made there will be more accidents and no doubt we will see a couple of them show up on this site.