We had an issue where the switch where the micro switch that we used to position frisbees before the shooter would bounce mechanically, ie occasionally it would detect two frisbees passing through instead of the one. The switch was set up so that it had a flexible surgical tubing extension that contacted the frisbee. We found the extra mass of the tubing would give it a higher inertia, and give it a higher tendancey to bounce.
We solved this by removing the tubing and by repositioning the switch so that it contacted a bent metal section of the lever, in tandem software also implemented debouncing code. (Which I think we disabled after fixing the problem mechanically)
As for what limit switch, in Australia we use:
http://australia.rs-online.com/web/p...itches/515735/ It is pretty much identical to the one that came in the KoP (except grey, and slightly higher current rating) and has been very versatile.
Tim