This shows a Popular Science review of the Glasspar V-20. Mentions 15 foot seas during the offshore run. No thanks.
https://books.google.com/books?id=rC...20v-20&f=false
And here is an advertisement for the Glasspar V-20
https://books.google.com/books?id=RC...20v-20&f=false
By 1967-68 Glasspar was advertising a different Deep V 20 footer. I guess this is when Wellcraft swooped in bought the design.
An actual Glasspar in the wild: