I wholeheartedly agree, with some personal experience. When I first got Eliana I was using a preventer to the rail like that. On a moderate wind day we happened to have a jibe go bad and back wind the sail. The boom flexed and bent like a piece of spaghetti. Nothing broke, but it sure came close, and could have been disastrous if it did. A preventer should ONLY be attached to the end of the boom.I recommend against using the genoa track as a boom preventer. Our preventer runs from boom end to bow and then back to the cockpit along the deck. (see Attainable Advenure Cruising for rigging description.) A large and expensive boat was lost a couple of years ago north of New Zealand when a jibe ripped out such a preventer from the toe rail, the boom ripped out the main traveller, and all hell then broke loose.