We used an epoxy filler., ran out of time as we need to get the painting going. Next year while waiting out hurticane season we are going to have thumper drop the keel for general maintenance of keel and bolts. It has never been done and she is an 1989 so definitely due. As far as the filler, I'll email thumper and post what he says for future reference. It felt like resin, very hard.
BTB, the boat looks great, rudder, skeg, cutlass bearing, ��. She is such a beauty in and out of the water!!