BayRaiders,
the mainsail+gaff halyard how it is attached to the gaff yard, I have now seen several different versions on production boats, and they are all not too practical. The idea was/is that the carbon yard is hollow and so as not to compromise it#s buoyancy, the yard should not have any through-hole.
Well what the heck I have drilled my yards. I reinforced the area of the through holes -on both sides- through glueing on thin strips of teak using Pantera sealer (Epoxy does not bond with carbon, while Sikaflex and Pantera do).
I then drilled the through-hole. To retain the buoyancy of the spar, I sprayed in a small quantity of PU foam, and while that was filling up and setting inside the yard I had inserted a wooden peg (oiled, so as not to bond with the foam). Very happy with this arrangement. Plenty strong too.