[Aardvark]

IF you are facing the back wall of the oven I put the heater nozzle? at the bottom right corner of the oven using a welded stand that the heater sits on to keep the output horizontal and I put an 8" vent with damper (Mcmaster-Carr) in the upper left corner. It circulates quite well, apparently.....

Do not use extension tubes on the end of the heater to get the nose inside the oven....It will give it that nice jet engine sound that will bother the neighbors blocks away. (I have already done this experiment for you) The heated air needs to expand or accelerate so I put the nose just barely inside the oven chamber. Problem solved...