has anyone got any views about foam sandwich construction dinghys - circa 1999.

In merlins or in general

Generally you are talking about Turner CT's  which were V good, possibly some early winders he took the mould in 1999 all very successful,  some NSM2's (34xx) from same plug but different builders were a bit varied, those sponsored by Welsh Harp were OK.
Earlier NSM1's  (3213 was the first)are Rowsells but could take on a bit of weight through Bilge there were some NSM2's (33xx) (Galactic Gnu was one)from Bob Hoare build ok but were not seen at the front of the fleet.