I haven't found it an issue with my BP nor has it been one with my daughters adult corn snake who is also in a T8. With my BP I only use enough substrate to cover the bottom nicely so it doesn't show. My BP has never seemed to want to burrow any although in his hides it looks like he goes around in circles and makes almost little "crop circles" in the substrate.
I use a little thicker layer of substrate for the corn snake as he likes to burrow just under the surface at times and has little tunnels all over the place before long.
In both cases with me anyway height of the T8's works just fine and haven't had any issues at all. I did have to play around a bit with the placement of my thermostat probe to get my temps just right. What ended up working best for me is running the probe along the hot side wall and leaving the probe on the surface of the substrate about half way along the wall not quite directly under the RHP. I've had to maybe readjust it twice from the snake pushing some substrate over it but other than that works great for me. Gives me a 90F hotspot, 75-77F in the coolest back corner of cool side and about an 82F ambient temp. Check all my temps with a temp-gun.