Here's some footage from Waves of Change that shows the wide tailed V Bottoms Mark Martinson and Bill Hamilton took to Europe in 1968...
You can see the tails drifting out in turns, and the general awkwardness of the V's. It also underscores how good those guys were...their boards were a handful to surf and they were still ripping!
Keith Paull's green round tail is noticeably more advanced.
The shot of Martinson at the 1:00 mark is clearly taken at a later date, when he was riding a more tuned in hull with a narrower tail.
Also, Mark trimming forward on his red V at 4:27 reveal his natural instinct to ride a more roundtail style of surfing. Beautiful stuff.
Here's the trailer to Evolution...
Much more consistent surfing by the Australians on their pulled in roundtails during that time frame.