Well, I followed the fix from another member (LukeP) for the sag in my Boler roof. Here are the steps and tools needed after removing the glued carpet interior.
1. Bought 2 aluminum stocks 1/8" x 2"x 3ft from Canadian Tire that I cut to the right width. I bonded these to the fiberglass with ClearWeld Quick Setting Epoxy, held in place by adjustable support rods from Princess Auto.
2. I then applied two layers of fiberglass(Bondo Fiberglass Resin + Mesh) extending 2" on either side of the aluminum stock.
3. Took the adjustable support rods down and finished the fiberglass in those areas. Light
sanding and done!
The aluminum stocks are placed 6" away from the roof vent on either side. No more sag and roof is much stronger. Should be even stronger once roof vent is installed. Fix might be 1/4" thick so doesn't affect headroom.