The volume could definitely be higher now, since the box sides are so bloody high that you can’t actually put anything in the truck without a ladder.
As a farmer and actual truck user everyone I know has a beat up farm truck from the 80s for actual truck use, modern truck is just a big car for comfortable city trips
The simple solution sounds like it should be shipping more panels to the rest of the world?
Solar panels are still excessively expensive here in Canada