Being vertical is not the problem. Some top of the line HT ovens are vertical (Jen-Ken Air Bath).
The bigger issue is the controller. It looks like a kiln setter type, which won't work for knives easily. You could change out the control for a knife oven type for about $500, but that raises the price.
9 amps at 240V =2160 watts. Ok, but not a fast HT oven.