Paul -
I have a '66 Williams Pitch and Bat that is very similar to my game. The '2nd lever' is critical as it helps 'fling' the ball with extra speed. On my game the there is a 'fast' and 'slow' pitch button (in addition to curve and knuckler) and the difference between fast and slow is whether or not the 2nd lever is utilized.
I was having all sorts of problems with my pitching unit until it disassembled it enough to clean (with alcohol) all the various levers and bushings on the pitching unit. Made all the difference in the world.
I will say there is still a fare amount of variation in the 'accuracy' of the fastball but I think it is working correctly and that it's just built in variance that frankly makes the game more fun. On my game, if you consistently throw 'slow' balls, you can really rack up runs, if you stick with the fastball and curve, it is tough to score more than a few. Most of my head to head games with friends are 5-3, 3-1, etc.