I would venture to say fiberglass technology in the 50's and 60's was still a burgeoning industry with a steep learning curve.
1964 in high school, my old 7'6'' Bing Surfboard weighed as much as a tank with rails like a stand-up paddle board. In those days (before the advent of surfboard leashes) I always had to chase that bad boy down whenever I fell off (which was more often than not). Needless to say it got banged up very easily and was totally waterlogged after one season of surfing. Paid $20 back in the day...recently saw a similar era board at a Longboarders Club meet for $1,750. YIKES!
I cringe at the thought (and death-defying danger) of being in a FG Spyder banging fenders with bigger race cars during 50's or 60's races. 