Setting up UTH and Thermostat.

I arrived at the conclusion that heat lamps are unsuitable for ball pythons due to the fact that they desiccate too much.

I already have a zoomed under-tank heater, but I feel it is too small, it's about 4x5 inches, and I keep my bp in a 20g long glass tank. What is a good size uth to get?

I plan to order a Thermostat from Zoomed. I assume this is a good idea, unless anyone has any objections/suggestions. Would this heat up my tank enough?

Also how do you use your uths? I hear some people attach aluminum tape so that too much heat doesn't go to the tank. Thanks a lot for the responses.