Tom Morey broke the mold when he named the 1969 Morey Pope pintail the "Stradivarius."
After the McTavish Tracker model of 1968, Tom took a hold of the MP design reins and developed the Camel series of shortboards...one of which was christened the Stradivarius.
Since the ease of longboard paddling was still a recent memory, the idea behind the severely hump-decked Camel models was to pack as much volume into a small board as possible. The decks were so radically thick -- 4 inches in some cases -- they had to be shaped out of custom blanks.
In a less extreme form, the concept of an S-deck proved to be valid, and builders utilized the concept for a number of years.
Of course, Bob Simmons was using S-decks as far back as the late 40's...
But that's not why we're here today...
At least one aspect of a recent explanation for the reverence of the Stradivarius violin involves flex:
"Dr. Tai’s team also found a property in the Stradivari violin samples but not the cellos: When they heated the wood shavings of the violins, they found an extra peak in oxidation, which implies a detachment between wood fibers. This detachment, possibly the result of centuries of vibrations from playing, may give the instruments greater expressiveness, Dr. Tai said, adding, “Top violinists often feel like these old violins vibrate more freely, which allows them to express a wider set of emotions.”
So, it would appear that the sound of the violins build by Stradivari may be, in part, due to the fact that the body flexes more than modern violins because they've been "broken in."
(Another perspective of the same discussion involves what is known as the "halo effect." )
Anyway, this is kind of an off-topic, tangential post...but hey, if surfboard flex can be justified by the flex of a 17th century musical instrument, why the hell not?