Bruce - thanks for the reminder. I am done and all that remains is to put the butyl tape on the edges of the fan and screw it into place. After finishing reinforcing with the marine ply I shaped and filled and faired Until everything was smooth enough to fiberglass. after sanding the whole roof with 80 grit I laid 2.3 Oz fiberglass down both sides and poured the epoxy to it using a flexible spreader to get the cloth saturated and attached to the roof with no dry spots or places where there was too much epoxy. Another coat of epoxy after the first hadnít finished curing but was not sticky or tacky to fill the weave.
Next, I built the frame to mount the fan. Cut out the hole in the roof through the marine ply and test fit everything before using thickened epoxy to glue the frame to the roof. Followed that with fillets of thickened epoxy to give a nice curve between the roof and sides of the frame before applying fiberglass tape and epoxy. This was followed by more filling, scraping and sanding until it was ready to paint
Then after sanding with 120 grit, three coats of System Three Yacht Primer all applied before each coat had cured...to avoid sanding between coats. Once the primer had cured, I sanded it and put on 7 coats of System Three WR-LPU two part polyurethane, 5 of white and two of clear glossy.
Here are some pics: