I repaired mine using aluminum flashing to make the form for the new floor. The fiberglass will not stick to the aluminum flashing. What i did is cut out the old floor and then i rivited the form in place. you will have to flare out the remaining fibre glass floor to get the new fiber glass resin to stick together. I used 6oz matting and layed 8 layers on the form and let it harden for a week. Then I removed the form and painted it with some black paint.
Good luck