Purchasing Pitching Machine

I purchased a single wheeled BATA machine (and generator) when my son was 9 and it worked great for two years but now we want to work on curveballs and pitching beyond 60 MPH (my son is on a competive travel team and is now seeing curves and high velocity pitches) I'm considering a Dual wheel type( we just moved to a new house with room in the backyard for a batting cage -- dual wheels machines aren't easily portable). I might suggest if you are serious (and it sounds like you are) to consider the Dual wheel machine. And if anyone has one to sell they can contact me also. Use the above e-mail address.