RE: Fiberglass Repair
A rather inexpensive core material like Nadia core will work fine for a roof top.
THe technique is to lay up the roof on one side only , on any flat surface (cover with plastic.
Then after 3 days when modestly cured turn it over and use whatefer you have as spacers to curve the roof to the camber required.
Usually a heavy plank in the center and two side planks will give a nice smooth curve.
THe outside layers are then laid up , and when hard , taken out to cure better in the sun.
2lbs per sq ft is doable but 2.5 is easier for a first time glasser as there may be some errors.
Friends and beer can get it lifted down the dock and up into place.