This is generally done with a micro switch monted on the recoil unit. When recoil is triggered the micro is tripped and the flash is activated. Also the flash on the HL's from the Rx 18 is a high intensity flash unit itself. I'm not sure the board is made to actually supply the voltage need to givre the proper effect. bubbajoexx would know much more about how to go about getting it done with out torching the board.