My 17m 1967 Phoebus C had balsa cored epoxy sandwiched GRP wings. Built by one of the ATAFLIEGS..iirc Stuttgart. Gave it an interesting polar as wing had a marker lower under camber profile which meant that at low speeds it was in laminar whilst upper wasn’t and high speeds vice-versa.
Some bright spark suggested that I took core samples to check for rot .obviously didn’t understand the implications of the hardwood nor its purpose in the construction.
My father built MTBs in the war and in the 60s commissioned a high speed hull mould ..both used formers with triple veneers glued to form the complex curves.
I designed a caravan using end grain balsa sheets for the infilling but there was a problem with adhesion using polyester resins during the moulding process…our competitors..Eric Birch,who moulded Prout catamarans for a while and made Jaguar yachts, went over to a special foam with appropriate glues which cured the problem 20 years later. Apologies for the pun.