[willy]

Ozzie been thinking about your querie while sipping some Jack, thats how I be doing my best thinking by the way.
The top cap, inner liner would also be part of the structural integrity of the later V's, I'm willing to bet a few bucks that the earlier designs without them had thicker glass and reinforcement wood etc. to give them the same structural integrity.
Just a thought, plus the glass matt used in earlier boats may have been a heavier weave or older style(heavier weave) thru the inner lay up for the same reason.