A slightly back-winded mainsail from being off course, being held tight in place by the preventer will exert little force from momentum even in moderate air, as it should not be moving. I doubt it would pull anything out of the deck, etc., just carrying the static load. I suppose the bad act is where a very strong gust hits the boat from the lee side. Such as a williwaw when passing Pt Conception on starboard tack, on a broad reach, continuous wind from the NW. Still no shock loading, however.
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