Sorry I missed all this, I've been super busy.
In my opinion, the flexwatt Jeff sells with his Boaphiles isn't very good. It's lower wattage and takes forever to heat up and doesn't heat up that well at all. I do NOT order my cages with his heat. I purchase my heat tape separately and install it myself. I have absolutely no problems with the heat doing it that way. I place the probe on a bottom of a 6-tier stack of 421D's. The t-stat is set at 90 and the flux is 3-4 degrees higher up the stack and the top cage reads about 90-91. I use 1 T-stat per 6-cage stack.
Heat panels are a great option though, from what I've heard- they work awesome.