Don it is so unusual to come across someone that has actually made sails as his trade. I understand that making a batten sail is overkill for what I am it putting it on but it has taken on a life of it's own and dragging me with it. I'm glad you confirmed the battens are thinner at the luff.

"There was a sail maker the used full size molds to set
: seam taper, you could use cardboard to build it or double stick tape and 3
: mil plastic drop cloth as a mock up, just use in light wind test."

I thought the above you mentioned might be one way to build a panel sail also.

And I also come across the block diagram for doing the same thing. The center is the foil shape and the 4 to 6 degree tapers allow for the seam width with an extra height of camber but when sewed together the sail comes back to the original camber because of the seam overlap. The cloth is over lapped and cut on the center which makes built in seam width and when it is sewed together it comes back to the original foil shape. Mathematically you get the seam width by the degree used. I thought I would make a model someday and try it. I have no idea if it would work.

John