Have you considered a pvc cage? I love my Animal Plastics PVC cages...I use them for boas, a carpet, and a BRB right now. I know many people use an RHP with them.. I believe you order the RHP from another source and AP coordinates with them to install it for you (might be pro products?, not sure).
My AP cages seem to hold ambient temps well and have sliding glass doors so you get good viewing also. I also love the fact that you can get a lock for the glass doors to protect your snake.
I would think a single RHP would be enough to maintain ambient and a hot spot, but you could call AP and ask them. Their customer service is great.
That said, the wait time is about 3-4 months, so be prepared for that.