I decided the best course of action for converting to a high top was to remove the roof and then do the modifications in my heated shop. Removal took about two minutes with a recipro saw with carbide blade.

Done. Scary how quick and easy this was!

Once in my shop I cut the top of the roof off.

I used smooth 1/4" masonite to make forms (forgot to take pictures) for the new sidewalls and applied one intial layer of 1708 fiberglass ioregnated with West System 105 epoxy.

Then I reinstalled the roof top.

I built a wooden cradle to hold the roof off my work table so I could work on it without distorting the roof's shape.

I used 1/8" smooth masonite to make a curved form section to close the front of the roof.

Front section has been laid up.

Still have a gap on each side to fill in.

Masonite forms in place for laying up the corner gaps.

Done. Well, except for sanding and fairing. The new sections consist of two layers of 1708 with additional layers at the edges and corners. Note that while the roof section of this hightop is 4" higher like the factory high top, it is longer than the factory hightop, meaning the front angle is a steeper pitch. My reason for adding a hightop is to provide a place to store 30" x 64" thin flex solar panels, and the ceiling space in a standard factory high top is too short to allow this.

These are the sanding blocks I fabricated for the sanding work I did on the roof. I have power sanders, of course, but rarely used them for two reasons - 1) The blocks allow for even sanding with no dips and swells, and 2) the blocks don't get dust all over my shop like a power sander does, even when used with vacuum system. Oh, and 3) the use of the blocks provide a nice upper body workout.(winking smile emoji here)

I decided that while I had the roof in the shop I would go ahead and prime it for painting later. I did final sanding with 320 grit sandpaper and then primed it with AlexSeal primer. The primer was thinned with the proper thinner and applied with the proper roller as per the AlexSeal directions. They claim that the roller texture would not show, but when I finished applying the primer, the rough roller texture was obvious. I was quite disappointed, but when I returned an hour later it had miraculously disappeared! Hurray! I am now optimistic and encouraged that the AlexSeal product will provide a good final paint finish for the boat exterior.