I have a Nacra 5.2. Its the Bridle wire attachment point. The shrouds on that boat attach right by the dagger boards.

Lots to upgrade on that boat but a lighter mast wouldn't be on my list unless someone had a nice one piece carbon mast for free...

I'm with Northsea Junky (who needs a shorter nick; "Diehard" would be an option ;-)

You can lift the lids off the bows with a strong putty knife and a chisel, just work a round methodically and 'feel your way' in order to not damage the hulls or lids (or your hands for that matter!).