Wow, that sounds like a scary day! I hope everyone pulled through.
I run redundant thermostats. I am in bad shape if both fail open, but that's not very likely.
Good to know herpstat sells ones that offer more protection.
I agree, and sorry I missed it, that you need two hides. One in each heat zone (hot/cool).
I run an RHP and UTH mainly for redundancy (I am a nervous nelly). The incremental cost was very low to add the UTH, so I did (both run off the same thermostat). It's a preference thing, but not necessary.
I'll admit that I thought RHP's were more for air temp and "shine down/sun like" heat (not in that order though). I never thought about it adding belly heat. It makes sense though, when you think about it. Well, I stand corrected and I am glad I learned something new today. I have seen many people successfully keep happy and healthy snakes in enclosures with just an RHP, but it never really clicked.
Thank you, as always, CloudtheBoa.