Question on heating and thermostats

I'm putting together a new cage for my BP (PVC with sliding glass front) and I have some questions on heating and temps. I've installed my Herpstat probe between the Ultratherm and outside cage bottom with the Herpstat set at 91 and its holding it steady. Inside I have about a 1/2 inch of bark and coconut. I have a temporary probe resting directly on the bottom and it reads 84; when I use IR gun on the top of the substrate it reads in the mid/upper 70's. I'm going to be putting in another heat source to raise the overall inside temp. The humidity is currently around 80 (I assume the high humidity is contributing to some cooling of the substrate?). I'm planning on a radiant panel inside for ambient heat. My questions are: Does everything sound ok so far? I believe there to be some heat loss thru the bottom between the Ultratherm and bottom; what would the normal increase of the heat be to get 90 inside on the bottom (is +6 degrees alot)? I wasn't planning on any fixtures and there are no holes in the top of the cage other than a long narrow one with a screen if I wanted a fluorescence light bar; is the radiant panel a good way to go, would another Ultratherm also work? And the last one; could I use silicone to adhere (embed) a temp probe and it's cable to the inside bottom, to monitor the actual temp of the hot side where my BP would be, keeping him from moving the probe?

I hope this hasn't been too long. Thanks for any help......

The heat lose is from the substrate being to thick. It needs to be a 1/4 inch at most over the uth. Reduce the layer of substrate and see where that gets you.

A rhp may be a good choice but if your room is near or under 70F it may not be enough depending on the size of the cage and thickness of the building material. I cant say for sure and can only judge by what I found with my large pvc cages. They are 4ft x 2ft x 15in and the rhp was not enough to heat them to what I needed. I ended up heating the entire room with a oil filled heater.

A light is easy to add. You just need to find one that the cord unplugs from the fixture. This will allow you to drill a hole just big enough to pass the cord through and plug it into the light.

If you are asking about a thermometer probe you can use silicone it down but you want to be careful not to insulate the probe where it gives false readings. If you are asking about the thermostat probe the answer is no as it needs to be outside the cage as that is the only safe place for it.

Substrate is likely too thick. Personally I have only found an RHP to add a few degrees to ambients not enough often. Lights often add far more so I would suggest a Fluorescent light bank be installed and an LED lighting system for nights, both give off more heat than you would expect and in my experience add far more to ambients than an RHP does.

"Radiant heating as a technology is more narrowly defined. It is the method of intentionally using the principles of radiant heat to transfer radiant energy from an emitting heat source to an object" Radiant heat does not heat air directly. A UTH is also a radiant heater as well. I have been experimenting with a top mounted (outside the enclosure) UTH instead of an RHP. Very similar but most UTHs are too low a wattage and run too cool to be used as a hot spot.