Yes aluminum tape for attaching flexwatt, just make sure you only cover the edges of the tape. If you cover the tape fully you can run risk of overheating and possible fire from what ive heard.
Dont be worried about flexwatt, as long as its on a thermostat it should not malfunction, just make sure your probe is secure.
I attach mine inside a tub so I know the heat has penetrated through the plastic tub and the snake is getting the full 92 degree hot spot.