Making a Heated Build Chamber

#1
So I don't actually own a gMax yet. I'm waiting for when they get their supplies and start filling the pre-orders. But I know misumi has that FIRST150 code to get $150 off your first order. And since it's good till the end of the month, I was thinking I should do something with it. Such as get the parts to make a heated build chamber! Anyway I saw they had a simple system to order an aluminum extrusion box:
http://us.misumi-ec.com/vona2/detail/110302285350/

If anyone could help me with best measurements to make a Build Chamber I'd sure appreciate it. Thanks! Otherwise I might just get a bunch of t-slots and cut them later.