backwoods professional

Don't know about the pro, but on my fatboy the charcoal would run 10-12 hours at 250. If I remember correctly, the smoker had a bolt pattern for a smaller caster, but it was nothing that couldn't be fixed by drilling a couple of new holes for bigger casters, so I would just buy the casters you want instead of getting them from Backwoods.

Pretty sure you can order the feet for bigger bolt pattern casters straight from BWS

I too do not have the "Professional" model but have the "Gater". I have found that I can get an unbelievable 18 hours on it by using Royal Oak Hardwood Chunk. What I have found is that the chunks are smaller, which I always thought was a bad thing, however it seems to burn consistent for me. I install my Guru on the back air inlet and light the coals in that same back corner. My charcoal is placed into the firebox and pushed back a little more tightly than loosely. Before I go to bed, I push the charcoal back again and fill the front. That gets me a very long good nights sleep+. Sometimes I have to choke the slide valve on the Guru if my temps run off on me but once it's set, it's right on. Again, I think the long cook times I'm getting are to do with the size and type of charcoal I'm using. Hope this helps. Good luck. I'd be interested to hear what cook times you can get as well.