And here are some skids of 'drywall'.
These are 2x4 blocks CNC'd down a bit smaller (about 3" wide) to give some gaps across the trailer width. Also very shallow grooves for locating the 1/4" square dowels. Then some very-slightly-gray paint.
The end decals were photoshopped from an internet picture and printed on standard paper, then fastened with double-sided tape.
These 'skids' were very cheap to make but definitely time-consuming. Would take 3-4 hours to make a full set of 12 to fill a trailer.
The grain of the wood and some of the splinters bothered me at first, as it was a clue that these were just wood. But they add a bit of texture that is growing on me. Besides, sometimes it's simply impossible to scale every detail, and I haven't seen any RC cargo like this before, so we must accept the results.
