How do you guys maintain mash temperature with BIAB in a kettle outside? I'm making 5 gallon batches in a turkey fryer and am really struggling with maintaining temperature. I've tried insulating with a sweater and a vest. Temperature drops 1-2 degrees C every 15 mins. I've tried keeping a low flame while stirring, but this is cumbersome and a little scary (worried I'll burn the bag). My efficiency has been low 60s.