I've done it both ways plus doing a patterned bottom on a canoe. No real preference, it just depends upon the hull design. The first kayaks I built were Panaches and Rob Mack suggested doing the hull as far as you could, then starting on the bottom and working up. The bends that would have been required prevented doing it the conventional way. It was difficult making a smooth transition from the bottom to the sides. Did a King and it worked out fine -- did one side of the football first, let it run wild then cut it off straight with a saw. The biggest thing to remember with a kayak is that no one sees the bottom except when you roll. If you don't like the way it turned out, roll faster. Even with the canoe, I'm usually the only person who knows there is a design there and after I load in the gear, I'm relying on memory.
Good luck and just relax
best
don

: I'm over half way done with hull. Starting to have to piece those strips into
: the "football" areas on bottom. Wondering (??????)...dang, it
: looks like it would have been WayEasier...to have started on the very
: bottom...the keep strip(S) first...and worked the way down both sides to
: the shear strips. That way both sides would be open ended and I wouldn't'
: have been trying to piece little puzzle pieces in? Besides...those shear
: strips would have to be planed later anyways. Arghhhhh....why does
: everyone work their way UP to the bottom instead of down????