Floor Plate over Gas Tank Soft

[RIKen822]

Removed the cover over the weekend. Found rotted out angle iron that had been mounted to bottom of the cover 20+ years ago. The existing squares are water saturated primarily due to two inspection covers that had been installed and not caulked around the edges. Also, the former owner boxed off the port/starboard sides with 2x6s and ran 2x2 across to help support the cover.

I'm trying to figure out how the new plywood/fiberglass gets attached to the cover.

How much of the old fiberglass needs to be cut away?

Does the plywood need to be embedded in resin (between the plywood and cover) or does the new fiberglass hold it to a lip that I leave during the cutting?

Thanks