Hey there, congrats on the new bp!
Yeah, definitely ditch the hot rock plan; they can develop hot spots and bp's have poor heat sense in the belly=burned bp.
A heat pad under the glass on the warm end is the way to go. Get a dimmer switch for the pad so you can do fine adjusting. Wall mart has nice digital indoor/outdoor thermometers with a wire probe(usually 10') Above the pad on the inside of tank is where you'll want to put the probe. Stick it to the glass just under substrate and now you'll know what the bp's belly temp is. If too hot, adjust with dimmer. Aim for 90. 95 is almost too warm.
The ambient air of the tank should also be known. Place a thermometer an inch or so off the floor in the hot and cool zones to spot check. You can see already why many of us like temp guns that we can point anywhere and get instant readings.
Your hot zone should be about 90, cool should be around 80 to 85. These temps will fluctuate during night and day and that's groovy.
For the hot zone, I recommend an infrared light. It's said bp's can't see that type of light. It can be left on 24/7 and won't be a "constant sun" inside the bp's world since the lack of night time will stress it out.
For the cool zone, you can just leave it alone or if it's too cool, get another UTH (under tank heater) with dimmer and set it on low (78-82ish). Too cool and you risk resp. infections.............
Probably most important, get a hygrometer and welcome to the Battle of Humidity! The humidity of the tank needs to be 50 to 60 all the time, and up to 70 or so for shed. 75 just makes me nervous.
While you're picking up supplies, get some duct tape. You'll need it for the screen top. Look in my album to see what I had to do to my screen to hold heat and humidity.
Tricks for upping humidity: water dish partly over UTH, misting with water bottle (not on floor), just read any post on humidity, it's a common concern!
Well, there's more, but I'll let some other people throw in a nickel.
Enjoy your new python! They are great pets. :wink: