they were also bolted in. With bolts strength is a function of friction - the bolts are strong enough but they should be torqued appropriatley to cause enough friction between the fiberglass and the stainless to not move under load. Bolts should not be considered the equivalent of a clevis pin.

Your rigger is probably right about the number of bolts. I few extra layers of fiberglass to stiffen the hull in that area may also be a good idea.

As a point of reference, my chainplates each have six 1/2 inch bolts holding them to fiberglassed in knees. Also, 3M 5200 tends to be too in-elastic for chainplates - softer, more stretchy caulk is better. I have had a lot of leakage around the chainlpates because of using 5200 - 4200 works better.

Boat is a Nordic 44 with a 64 ft mast.