No, I don't think it can ever be too big, not for a juvie/adult cham. For a young baby, perhaps, but not for an older one.
You can always cup feed some of the food to make sure he's eating something.
I am currently keeping my little Mt Meru jacksons in a fairly large enclosure. 48' x48'x 72'. Most of the bottom half is covered with live foliage. -----Can an enclosure be 'too big'?
One of the best things about owning a Cham is that in a larger environment they are pretty active, depending on species. Especially if there are a few free ranging crickets lurking in the bushes. All of the sudden you see so much more of their natural behavior and activity.