40 to 60 watt would be fine. Obviously the higher the wattage, less work the rhp will have to do. Most cages I have are 3x2x2 and I use 60s on my rhp. No problem keeping my ambients where I need them (various) 80s. FYI, whatever ambient temps you desire will not just be your cool side but your whole cage
0.1 Emerald Tree Boa (Northern)
0.1 Green Tree Python (Aru)
0.1 Pueblan Milk Snake
1.0 Mexican Black Kingsnake
1.0 Pied Het Lavender Albino Ball Python
1.0 Yellow Phase Eastern Hognose
Sooo....I need a thermostat that controls two heat gradiants in order to have consistent temps for hot side and cool side? I had a cheap stat that failed and killed my last snake. Not again! Gonna set this one up right. Want to control temps on both the belly heat on one side and the RHP for ambient on the other. My house gets too cold in the winter to go with out something for the cool side. Looking for hot side around 94 and the cool side around 84. Sound right? Obviously I don't want to spend more $$ than I have to But I also don't want to lose another pet.
You want those temps about 5° lower on both sides. Also, your rhp is going to make a hotspot underneath it. By placing rhp on the cool side you are effectively eliminating your temp gradient. I’d try the RBI 40watt or talk to Bob at Pro Products and see what panel of his he would suggest