Adding another section of pipe and getting rid of the bend will create a better draw and make the venturi unnecessary.
As long as smoke is coming out of the stack even with the damper and draft closed of you shouldn't be getting any combustion gases back flowing into the tent or space that's being heated.
I really think you're searching for a problem to apply your solution to.
Yep.....seems like a solution to a problem that doesn't exist.....as long as you have enough stove pipe for a good draft the smoke all goes up the stack....sorry but you did ask....
