arduino in potting

Anybody here ever fully potted an arduino (any model) in potting? Say, if you wanted to make it waterproof or damage resistant. I want to pott my arduino uno about an inch thick all the way around but I'm worried about heat & thermal runaway. if that won't work, would the nano?

The linear power regulator on the board is pretty easy to solve -- don't use it! Get an external DC-DC converter with 5V output, or a good external regulated SMPS, and wire it to 5V on the Arduino. That should cut the amount of heat generated on the board well down.