The join is the weak spot and supposedly there were cases when the hull separated from the deck under severe conditions. If that happens and the join is at the sheer, your boat may still be somewhat floatable, depending on sea conditions and degree of the damage. If the seam fails at the bottom of the boat, it is almost guaranteed to go down. Also, the bottom of the boat gets scraped a lot, you don't want the weakest spot to become even weaker.

: Is there any particular reason that the two halves of strip boats are joined
: on the sheer? Rather than separating the boat into a deck and hull, why
: not a left and right half?? (or to be proper: Port and Starboard)

: Just occurred to me, and I couldn't see any immediately obvious reason is
: all...