Getaway Masthead removal?

The luff track on a Getaway CompTip split, so we ordered another one. New instructions say to install from the top by sliding the luff track down in the grooves (old way was to push on side to side first by inserting one track and then pushing).

We can't get the masthead off. We drilled out the rivet and have knocked at it from below with a rubber mallet, then a real hammer with a block of wood. How hard can we hit the masthead? Anything else we should try?

The front of the comptip has the halyard lock - those rivets also need to be removed - that's part of the mast head - see this photo:

_________________
Jacques Bernier
http://www.hobie.com/
http://www.facebook.com/HobieCatCompany

Thank you! In drilling out the other rivets, we caused a hairline crack in the fiberglass that goes to the top. Would a little fiberglass repair at the top of the comptip be strong enough? Or are we looking at a new one?