So, armed with Trisnake's very helpful information I have tried another configuration: I put the RHP all the way over on the the cool side and let the UTH handle the temp for both the hot spot and the air temp on the hot side and it WORKED!

Sort of.

By that I mean that I got the air temps that I wanted, but I've run into another problem, that I could use some advice on:

In order to get the air temps that I want (82 deg F) my RHP heats my newspaper substrate surface to ~96 deg F at the hottest point directly under the middle of the RHP (according to my IR heat gun). The floor below the substrate is only in the mid 80s so it's not like there's an awful lot of this heat energy at the high temp, but I'm a newbie so I'm concerned.

Is an above acceptable substrate temp (with a very low mass substrate) on the cool side ok so long as the air temps are fine??? Mind you these temperatures are all being generated from an RHP so it's not like I'm generating scorcher temperatures underneath the snake that would burn it's belly if it sat there. Is there anyone else on here who uses newspaper with an RHP? Or even just an RHP? Do/did you experience this higher surface/substrate temp than air temp situation? If so what did you do?