Rockter is also sailing a full keel boat with the rudder directly abaft the prop. He will, with that set-up, generate turning moment. The faster the boat is running down-wind the less effect the prop is going to have on the rudder; that is until you begin to round up, losing way, and then she'll start forcing the stern around.
I am not against having the motor running for possible assistance, but i do feel that you'll generally have your hands full with working the sails. I'd say that Cam's procedure seems about the safest.
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Wm. F. Buckley, Jr.