The chute and firebox is most important part of that style cooker. Take your time and figure out the measurements of the box you already have and build from there. I don't have any Experiance cooking on a Backwoods style cooker so I can't say which is better. I have just over 70 cooks ( all logged in a notebook for reference) on stumps clone and the chute clogged on me 3 times. I caught it in time each time and hit top of charcoal with a fire poker to get it to fall. It will run for 23 hrs on about 16 pounds of RO lump. I also use an IQUE 110 on it. It holds temp the entire time.
My arsenal, Stumps Clone, Two Modified offsets, open pit with grate and rotisserie,UDS, and a free to me Weber One Touch Silver 18.5" kettle