moody pb used to do it, i asked him how to and he said this:
The switch install is pretty simple:
Desolder the optic switch, and find the two pads that were the receiver part of the switch. Do this by shorting the pads, and watching the shot counter while the board is powered up. The pads are laid out like this( : : ) It will be one of the pairs of pads close together. Once you know which half was the receiver, just solder a lead wire into each hole, and run them to the micro-switch. The connection on the micro-switch must be in the Normally Closed, or NC tabs. The switch will have three poles, one NC, one NO, and another that isn't labeled. Use the non-labeled one, and the NC for the wire leads.
As for mounting the switch, I used custom made plates, and a 2.5mm by 10mm stand off to locate it correctly behind the trigger tang.