I would suggest buying a real encoder, like the GroovyGameGear or Ultimarc boards. I wish I had known about these when I started out, but I ended up hacking a couple of old Gravis USB gamepads. Not that the gamepads don't work, but they were a royal pain to map, hack and wire. I also ended up wrecking one of them somehow (good thing I bought 3). A proper encoder will help to mitigate these problems.