Another thing you can do (if you want heat rising from INSIDE & near bottom of the cabinet) is to use a heat cable (on a thermostat!), the kind they use to
prevent pipes from freezing in winter. You can install inside a perforated pipe too, but either way attach at intervals to the sides (not flush against the sides,
but like the way you hot-wire a fence...with insulators that clip to the fence). I did a large cabinet like this many years ago for a Taiwan Beauty rat snake, &
it worked very well. The heat cable was installed about 12" from the bottom, so the "cool side" (w/ water bowl) was the floor, with heat that rose up into the
basking branches...beautiful snake & beautiful display. Cabinets can be fun...I also installed a light, recessed in the top- not for heat, just for light as needed.

Of course my snake was arboreal, while you want a more horizontal habitat...just throwing the idea out there though. I had so much fun customizing that
cabinet, but better yet, the snake seemed to like it & stayed healthy. FYI, I used side panels of perforated metal for more air-flow in hot weather, and I had
wood panels that fit over them to keep the warmth in the cabinet in winter.