Without knowing age or genetic background it's hard to say. If he is 2-4 years old, his growth will certainly slow.
I would personally go a bit larger. I think something 18" tall would be good and you could keep the 48" footprint and go 30" deep.
A T-8 is doable, but having an active BC is worth a bit of extra $$$.
They will display a wider range of natural behaviors when given options.