its not really that bad on the elbow. its all about the pressure of the fingers. add more pressure to your pointer finger and the ball will cut across. i used to throw it at age 10 and it is a great pitch to have. if you have a slider to go with it or a sweeping curve it is even better. Also a quite effective pitch is the splitter if you can control a lot longer to learn than a cutter or a curve.
Dipre- Did pettitte really try to throw a "pencil straight fastball." HELL NO the situation called for a pitch with movement. the ball moved into the hitter not away which his pitch did. Plus you are the only lefty that i have ever heard of that can throw the ball perfectly straight. Greg Terhune a kid i caught for years who is going to Seton hall on full ride baseball scholarship can't get his fastball straight because his has a natural tail. his does move about a good three to four inches. It does matter how hard you throw. if you are throwing a ball in the 70s the tail can be taken away easily but at the id to high 80s its nearly impossible. i know four lefties who have so much tail and they cannot control it.
Spudboy- i don't think i can type the perfect english that you can understand. lol.