PTP,
first off, those daggerboards look longer then stock. I could be wrong though. Second the handles are the old style so like mid 1990's blades. New blades were somewhat stronger.

When you are sailing in big wind ie 18+ you need to bring the daggerboards up 6-10 inches upwind and reaching to reduce the stress on them. This is especialy impartant if you are sailing heavy ie 350+ lbs of crew weight. The boards will last much longer and you don't need that much board down anyway (plenty of lift).

What realy breaks those suckers is reaching in waves. Launch off a wave when you are flying a hull fairly high. boat crashes down and the leeward board hits sideways.

Cheers,
Eric