: - is there an ideal size for a table to build a kayak on?

I build on a pair of original interior doors from a house built in 1951. They sit on sawhorses.

: - should the table be the length of the kayak?

My builds always hang over the ends.

: I have also read a fair amount about the butt joints and I am going
: to experiment with some scraps by adding a 1/16" spline and
: probably only using glass on the inside.

Experiment if that makes you happy. I think most of us here dabble in changes.

:The main factor seems to be the strength of the joint.

The butt joint will be plenty strong. I surf my butt jointed Pygmy Tern 14 often and have endo-ed it pretty hard with no problems. I built Nick's surf kayak from plans. Instead of butt joints the plans call for replicating the puzzle joints by hand.

I first drew and cut the male end and then used that as a pattern for the female end to help ensure a better fit. I cleaned everything up with a Dremel tool. It turned out perfectly. This surprised me because I am not a very exact person when building and prefer to smutz it up with thickened epoxy and then paint the hull leaving the deck bright. These handmade puzzle joints had virtually no light leakage when backlit with a 100 watt hand shop light.

Maybe you could draw your own puzzle joints on your project. Nicks surf boat has survived many endos, collisions with other surfers and abruptly ended side surfings where I simply ran out of water and hit the sandbar.