Your cage heat should be around 80 degrees, 75 the lowest at night. I've never used flexwatt on an aquarium, but I am figuring that it might get a little hot. Flexwatt transfers heat much fater than the heat pads. As you expand, just a word of advice, snake racks with bins are a much better bet then tanks or enclosures in my opinion. Throw on a herpstat and you pretty much have a perfect environment for basking, ambient heat and humidity. I did the glass aquarium and it was just too much work getting everything right.
Good luck,