I am using HALF a 55 gallon drum, and obviously not filled to the top. I have it sitting on bricks with the drum just half an inch off the burner. I knew it would not do the job on a full drum, but would guess I am using 1/3 and with a piece of metal on the top though it could handle it, did not happen yesterday. I did use this last year with a couple changes, a little less water and it was summer. Was pretty cold yesterday and guessing 7-8 gallons more water.
When I switched to the pot that came with the burner, worked great only drawback was could only do 6 traps at a time.
I need a big burner.
Try getting a 15 gal steel drum. The kind that hold grease.
Check with those quick lube shops.
The drum is usually lined with plastic container holding the grease.
They may have one laying around useing it for a trash can or waiting for someone to come get it.
Otherwise they junk them. Doesn't hurt to ask? May have to give them something if there is a deposit on the drum.
You could also ask at a repair shop that does lubes and oil changes.