Some people do like to give their rhacs more space and that's fine. An adult will pretty much use as much space as you will give it. The only time you need to be concerned about the size of the enclosure being too big is for hatchlings and younger juvies--they do need something smaller so that they do not have trouble finding food. So for instance, I would not start a hatchling in an enclosure that large--start with a kritter keeper or something similar and move it up into a large enclosure when it is big enough for it.

Temps should be between about 68-78 degrees, but at the lower temperatures they do tend to eat less and be less active.