Just went ahead and bought the 30ga. This is mostly an experiment, I plan on building a much larger oven in the future, so we'll give it a shot!
My plans with the fan is to place it at the bottom faning towards the door from the back, this way, it will not blow directly on the piece I am curing. I will run a 5 or 6" dryer vent hose up to the top for the input. Sound right?