Solutions to problems are easy. Coming up with a solution that doesn't create three new problems is the trick!

Yes, that's absolutely right. But just taking a step back, all things being equal a "full-round" fixture is inherently more complex than a "half-round" fixture. For one thing you need some way to support it - you can't just put it down on a table. if I understand the history correctly, the strip-over-form method was first developed for building canoes. A canoe hull is a "half-round" shape, while a kayak is a "full-round" shape - more like a fuselage, really, than a boat hull.

Given that the kayak needs to be built as two separate components anyway, it seems like the most straightforward approach would be to build each component on its own half-round fixture - that building both components on the same full-round fixture adds considerable complexity. That said, there may well be some aspect of construction that requires the full-round fixture. It's not immediately obvious to me what that would be, though, which is why I'm asking the question.