Here's the measurements of the RHP's I purchased from Rich at RBI: 12.5"x22.5x1.75. I needed to go with the 80 watt ones due to the weather conditions here in central Oregon. Someone living in a more moderate zone would purchase the smaller one. When I get the AP T20's, I'll go with the next size up.
Temps: Ambient= 83F; under the hide= 83.8; on the middle level toward the heat panel= 89.9; on the middle level away from the heat panel= 81.9; on the floor= 77.1-87.9 depending where I shoot the gun in relation to the heat panel.
You're making me work!!!!