I know this'll cost a lot of money, but IMO belly heat will NEVER get you the desired temperatures in a room in the low 60s.

The best way to do this is to get a space heater and get the room to the 70s.

If you don't want to do that, IMHO the best way to go about getting the right temperatures is to an RHP in a nice plastic cage, like those from RBI (they sell RHPs as well as cages).