Greg
Yes I found the same thing with the tank height on the Cardinal,
ended up with it a long way above the engine venturi,I was running an
11x4 Hawk wood prop with a Smith T/muffler,I think this was to restrictive
did not have a light weight tube muffler that wood fit,but the APC 10.5x4.5
helped , 10,500 rpm ground release.I had run mine in as per the instructions
gets better with use.
Will use it in the Brodak Vector when its built,( wing is done )