isn't this the job of the two part epoxy? , to seal the tank, this was my understanding from other plywood and glass tanks.
Steve
The 2 part epoxy goes over the fibreglass matting ( or not ) ... it is up to you really ... by putting the fibreglass matting down you get a stronger finish ( you dont have to use the matting ... you can just put the epoxy right on the plywood too )
Cheers
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Steve
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