I tried Vaclav's technique for treating fiberglass edges, and it worked so well, I thought it might be helpful to document it here for those who may not have tried it.

The attached photos read like text, left to right, down a line, then left to right again.

Photo one shows the final layer of glass on the hull bottom. The top edge of the masking tape was placed exactly where the fiberglass edge was to be finished, and the glass was epoxied over top of the tape. I attached strips of garbage bag to the bottom of the tape to mask the hull below. The epoxy was left to set to a firm but still flexible state.

Photo two shows the tape being lifted until it was just hinged at the tape boundary where the glass is attached to the hull. I lifted the tape until I just started to see a few of the fiberglass threads along the tape boundary turn white. This is barely visible in the photo.

Photo three shows the utility knife position for cutting off the tape, excess fiberglass, and masking plastic. Note that the blade is bent so that the cutting edge is more or less tangent to the glass surface. I found it helpful to gently pull the free end of the tape with my left hand while cutting with my right. If you get it right, the resulting glass edge will be tightly beveled to the layer underneath.

Photo four shows the end result. Relatively little work will be required to finish this edge.