If you were closer, I'd offer to give you a hand!
I built one for my old boat, and will be building one for the project I'm doing now.
On my old boat I made s wooden frame to wrap around the coming. My coming was about 2 1/2" high so I made the frame a little higher. I then used ribs across the top, sheeted it with 1/4" exterior ply, and about four coats of paint. I agree on the fiberglass cloth though for longevity. Use epoxy. Don't use polyester resin! Then a couple coats of good exterior paint.
To attach, I cut the heads off of two bolts that I installed in the framing along the front. they acted as pins which in turn, lined up with corresponding holes in the front coming. Then I had two hasps, one on each rear corner of the outside framing. I then installed tow eyebolts that again corresponded with the hasps. Worked pretty slick.
Your difficulty is going to be in making the rounded front. Certainly not impossible, just will take a little work. I would make a pattern, then laminate several thin strips around the pattern.
Whatever you do, good luck! and keep us posted.
Jon