My cages sit on the 8" stand made by AP, it is made from the same 1/2" PVC that the cages are. Before I got the 8" stands I used the pastil tables with fold out legs and TV tray tables lol. the Flexwatt when regulated by a thermostat shouldn't get much over 100 degrees ever. my hottest thermostat setting is 102.5 right now. While I wouldn't trust that sitting directly on my carpet... I would put it on wood or most plastics.

As you can se my cages are stacked on top of each other, and there is flexwatt sandwiched in-between them. I haven't found any need for an air gap or anything like that so far. This is because the thermostat probe site in the slop in the bottom of the cage... so it would detect any build up of heat and turn down the power going to the flexwatt.