Yes. And it's easy.
To begin with, there are four hex screws at each end of the lid: two 8 mm screws attaching the RamBox lid
hinge to the truck (location "A"), and two 10 mm screws attaching the
lid to the hinge (location "B"). See image below.
View attachment 4393
Don't bother with (A); there's no play in those, and it appears there are rivets next to them as well.
However, if you loosen the 10 mm screws at location "B", you'll gain 1/4"-1/2" (or maybe more) of adjustment between the lid and the hinge at each end of the RamBox lid. In other words, you can adjust the RamBox lid inward (towards the bed) or outward (towards the exterior of the truck) a pretty significant distance.
This is not a 'miracle fix'. For example, the RamBox lid latch does not have any exposed adjustment. It looks like you could get to this by removing (5) pin fasteners in the vicinity of the latch mechanism, but who knows what else you'd get into after doing so. Mine is 'good enough' without digging into it further.
View attachment 4394