I also have a 13kg one too. My calculations using that helpful online tool said this would be perfect for a reverse flow. But i was thinking about just using the 47kg as a vertical. With it cut into three sections, one for the fire box, than some sort of water heat spreader and than two other sections for taken apart/storage and mopping etc.
The only problem i can see with this is that i might have to bend the ribs as the tank/cylinder is only 15in in diameter. I think this would use less fuel and possible easier to make.
But i'm not bothered a offset taken up more space, and it being slightly more metal in construction.
i was also thinking of a offset vertical and having the firebox and the smoker on the same level, where the smoker connects to the fire box there will be a gap underneath, this gap could be used to keep food warm?
Just looking for some input, ideas and thoughts.