Hi Mark,
Given that youT is arboreal it will be perfectly fine in the enclosure you have now. The following rule of thumb applies to the size of the enclosure your T should be in:
Terrestrial:
Width = 3 x the T's DLS (Diagonal leg span - measured from the left front leg to the right back leg)
Height = 1.5 x the T's DLS.
Arboreal:
Width = 1.5 x the T's DLS
Height = 3 x the T's DLS
Your enclosure should also have a tall cork bark that the T can use as a hide and to climb. I lean my cork bark against the side of the enclosure to give it some stability so that the T won't fall and injure itself if the cork bark falls over.
The above is by no means a law but only my opinion on how I keep my T's. Some T keepers might keep their T's differently , but this works for me.
Hope you enjoy your new T.