What size of rhp

Looking into a radiant heat panel for the animal plastics T8 setup (48x24x12") my Boa has the 80watt one in a 48x24x18 just wondering if the 5 less inches of hight would mean I should get the 40 watt one (from reptile basics) would be used for a ball python.

I would just stick to the 80 watt. You will have it running on a t-stat so it's not like its going to run too hot.