The instructions for my Hurth V Drive say: "To lock the propeller vertically in line with the keel, mark the coupling and POSITION GEAR IN REVERSE. This will prevent slippage and damage to the clutch." I've been in the habit of leaving it in reverse, probably left over from 'the old days' growing up with a fixed prop where you HAD to leave it in reverse to keep it from spinning. I've put about 20K miles on my Nordic 40 with the clutch locked in reverse so it doesn't seem to have harmed anything (That said, I was interested to see RoyHB's post "the official word from Yanmar" to leave it in neutral. It appears Hurth contradicts Yanmar).

It appears shifting it to reverse to stop rotation, then back to neutral, works equally well. I sail in Maine, and frequently sail on & off the mooring, and I'd be a bit concerned if the Flex-O-Fold prop were to flop back open at some point and then snag a buoy before I realized the prop had come open.

It's an interesting discussion, will watch what others have to say.

Max