Hi,Evil Dog.When I was designin' mine.I printed lots of pics of cannons then checked with a protractor the angle of the tailpiece to the ground and found that nearly all were running about 22 1/2 degrees.then I slid a piece of wood similiar size up or down the axle timber till I got it to the right angle.I guess you'd call that 'backards engineering'.Good luck-hope it helps.Badger Bob