The fact of the winchman spinning has never been a great problem in my experience. Most winchman manage to get themselves facing forwards when it matters by leg movement. The purpose of trawling the winchman in the water on the run in to a sea rescue is so that he is stabilised facing forwards when he makes contact. Normally the winchman and rescuee are stopped just below the door on the way up so that any spin can be damped before cabin re entry. In my own experience on the cable, whether you spin or not is subject to so many variables of winching height/wind etc that trials as John Farley says would not produce repeatable results. However the worst case scenario always seemed to be no wind and high hover. Personally I was more worried about getting a static electricity jolt if the guy on the ground/water reached out before I was earthed.