I have been using Animal Plastics stackable cages, and I love them. Great humidity and all. Well, they've switched from using heat cable to flexwatt heat tape. Even though I loved my cable, I thought I might try out the flexwatt on this one since I'd never used it before. But now that I have my cage in, I can't get it warm enough. Here's the deal:

Cage is 3' X 2' X1'.
I am using the 11" flexwatt on one side of the cage.
I have the flexwatt on a thermostat, the Zilla temperature controller with probe (pic here: http://www.herpsupplies.com/images/S...Controller.jpg)
Average room temp is around 70, give or take 5 degrees because my house isn't all that well insulated. (Despite this though, my cages with heat cable are just fine, on the same kind of thermostat, and in the same room with the new cage.)
I got the cage set up yesterday afternoon (no snake in it yet--trying to get it up and going at proper temps before I move him), and it has been running since then.
A ball python is going in it, so I am shooting for an ambient temp of 85 and a hot spot of 90, but I can only get the ambient up to 79, and the hot spot is nowhere close. And my thermostat is cranked all the way up.

Any suggestions on what I can do to get my temps up where they should be in a stackable cage?