ive been a field mechanic for over 15 years, every box i've used in a service truck self destructed eventually.
what i found over the years is, you really need to secure the box to the truck to avoid the twisting and racking of the box frame.
my latest setup is secured through the bottom of the box in 3 or 4 places, and the back of the box is secured in 4 places as well. i havent seen any more cracking or twisting in the past year or so.
pics are from a previous truck, but the new truck is very similar.
