I would build your own rather than get the one off CL. The access isn't all that good and you can never truly disinfect a wood cage.

For now, you could use something in between and work on building his permanent cage. I had my yearling in a 30g long tank that was planted with a soil substrate. This worked great for her until we took her out to put in the rack. (She's got attitude issues, too, and this makes it easier to work with her.)

Jungles like to climb so I think that taller is better than long. I'm not sure just what size would be good for an adult as it's rather variable how big they can get. I'd look around they house and figure out where you'd like to have him when he's bigger. Then build something to fill that space.