I had a setup where my todds models 10x4.5 electric propeller was turning about 4000 rpm and was pulling about 10.75 oz of static thrust. static thrust is the most important element in my application. i now have the propellers inside a ducting tube. the tube is 11 wide (1/2 inch clearance on each side) and is two inches long. the propeller tips are 1/2 inch behind the front of the tube, giving me 1.75 inches behind the propellers. how much more thrust will i gain by this? any good estimates? this is critical for my application