i think that enclosure might be a bit small for that t.
For terrestrial t's the rule of thumb is that the length of the cage should be 2.5 times the t's leg span, the width should be 1.5 times its leg span and the hight above the sub should be 1.5 times the t's leg span.
So i guess with arboreal, and i may be wrong, the length should be 1.5 x the t's leg span, as well as the width, and the hight about 2.5 x its leg span. Thats what i would guess.
i go something a little bigger then 12x12x12.. maybe 15x15x15?? (thats what i have) but i like giving them room to move around.. if you're simply looking for something comfortable for the T then 11-12 ish should be alright.. i'd say what you have now is slightly on the small side..