I recently acquired an almost new Portable Buddy heater. My previous heat source was a Mr. Heater butterfly type that was fixed on a 20 lb tank. The only place it would fit without burning anything was in front of the holes in my Frabill XLT. I did the same with the Buddy until I got lazy one day and left it behind the seat. It worked much better as the heat had to go around me to get to the vent (the only vent in my older portable is the door), resulting in using a lower heat setting. It also seems to help with the drip as it does not melt the ice resulting in much less moisture.
All in all, Heater in front:
More moisture
More propane used
More obstruction
Chance of burning line on heater and losing fish!
All these problems reversed if placed behind you!