When I replaced the Rear bath of my Tradewind (the toilet fell through the floor) I replaced the peaces on eather side and than fitted a peace in the center. I made templates from construction cerdboard to get the cerve right. I used an abrasive cuioff wheel to cut off the boalts in the channel. I simply slid the new parts in the channel and used fiber glass tape to hold in place. After the floor was installed I crovered the intire floor with fiber glass matt and epoxy resin also theated the peaces before installing with epoxy resin payimng close attention to the edges. I used 1/2 in exterior fir ply for the floor and the new holding tank that I had to construct. The glue on exterior and marine is the same.
Jim Smith
1965 Tradewind(The Silver Abaltross)