Hi green-boat
am I right, any winch system probably uses a motor with gear reduction, and can't be driven backwards? So it really doesn't matter what you use, a simple switch on any channel will do the job. If you trip the winch to run one way on full channel in one direction and run the other way on other full extent of the channel, you get the desired effect.
Thats what I intend to do with my mr Darby. The easiest way (low tech) is put switch af full left and full right rudder, so that the winch only runs in these two positions. The high tech way is to use a microprocessor, and monitor one channel for max and minimum signal (1msec and 2 msec) and run the winch motor only as long as that position is held.
I am doing this, but to be on the safe side, I also intend to monitor the winch motor current. If the motor stalls for any reason, the current will rise and the motor will be turned off.
Paul