John, those old wooden T's are incredibly beautiful! And I agree with Wouter that wood is still an excellent material. Wood fibers are superior to glass when testing on repeated cyclic load. (The glass doesnt fail, but the matrix often do, I believe).
Wouter, I do think that plywood (if that is what you used) can delaminate..

I am wondering a bit tough, as the T was a plywood design. Are todays composite mass produced boats heavier than a ply design would be? Are they no stiffer than a ply boat (with comparable beams)? Are the glassfibre boats just a economical question?