The Jett 40 on a cardinal in not reasonable at all. For one thing it is not capable of running well at the slower speed that you need to fly the pattern. The jet 40's recommended prop is a 10/6 at 16.5K. If you purchased a venturi from Dubb it is for a bladder as it's entirely too big for suction. Richard Oliver does work on the new Bar Stock Jetts and has smaller bore venturi that might do better for you. Still in it's stock configuration I don't see it happening. If you have your instructions you will see that Dubb recomends rpm,rpm,rpm, don't lug the motor. Dennis