A T8 will work fine. I plan on a T8 for my BP and either a T10 or T13 for my sunglow BCI. Thought about a T25 for my BCI but shipping would be $227. Figure I got time to decide as I don't plan to pull the trigger until early summertime so I don't have to worry about the cold. Anyways the key thing about the height is how hard will it be to maintain ambient temps. That's the biggest thing you need to look at. For example heating a 12" tall cage will be much easier than trying to heat a 24" tall cage. Another thing you can do is if you are getting an AP cage, just add a shelf which will add more floor space and give your BP something to climb on assuming it likes to climb.