You've got a strange retic there. First, at 2 and a half he should be well over 13 feet. Second, Arboreal behaviour, when provided the opportunity, is very common with retics. I would say you had an inadequate temperature gradient in that enclosure that made him not wish to go up there, unless he did so at night when you weren't looking.

What is your definition of "pumping full of food"? Have you had hime since he was a hatchling? The first year and a half is very important for establishing a healthy growth rate and is overlooked by many for fear of being labelled a "power feeder".

Chris