I was having the same problem. With the heat tape + RHP's I found it difficult to get them to work in harmony together. I also have a divider and I put my RHP's right next to each other in the middle of the cage, only separated by the divider. Underneath I had a piece of 12" heat tape centered on the middle of the cage which gave me ~6" of heat tape on each side. I was fighting getting the temps right using both the RHP and the heat tape. I got tired of trying to get them to mesh so I removed the heat tape and am now using only the RHP's. I have my probes hanging on the back wall of the cage centered on the RHP, but not underneath it. I have my thermostat set at 85 or 86 and that keeps the hot spot between 90-92° and the cool side about 10 degrees cooler. I am still considering trying to run both the RHP's and the heat tape, but I'll need another thermostat. I am also toying with securing the thermostat probes so they hang directly under the RHP's and seeing how that works.

Btw, my RHP's are the pro products 40watt 12"x12". The surface temp of the RHP's is often around 113-117° to keep the hot spot around 90°. The room they are in in the winter is about 65-68°. The reason I am thinking of trying to run the heat tape as well as the RHP is that I'd be able to lower the temp of the RHP. I am afraid that my snakes may come in contact with it and get burned.