Always use a thermostat with any heating element, especially when you're using RHP and CHEs and having them sit IN the tank!

I've not used one myself, but I believe RHP probes you use like a CHE probe; have them half way along the length of the enclosure a few inches height off the substrate and have them set to the temperature half way along your desired gradient (for a BP, I shoot for ~84 degrees to make up for it being a slightly cool room). Hope someone can confirm, though!