My ply tub is looking rather tired its had a lot of use and its also been hacked about with experiments to get the balance right so I am now looking at replacing it with a GRP tub, I have done quite a lot on small GRP projects but not as big as a yacht tub so I would appreciate any comments and pointers on what I am hoping to do. Intention would be to build a foam/timber/ plaster plug around my chassis, when finished double sided thin sections would keep a foam inner, flat single sided sections would be released from the plug. I have used 300gm CSM in the past and thought about using 3 layers with extra reinforcement for mainsheet mountings etc, then topcoat for a finish. I am building it primarily to get a better shape than my ply tub and more durability but it would be nice to save some weight if poss, can anyone suggest what weights/layers of woven or combination mat might be an alternative?