Okay Marcus, I see what you are getting at.
Doesn't overlapping the cloth to such an extent create an anomaly in the stretch and flex characteristics of the sail though? I know that there is a batten at this point. So does that mean that this batten would need to be slightly lighter than would normally be used?
After all, you have now got one point in the sail which has two layers of cloth glued and stitched together (possibly with some sort of film or re-inforcing) plus a 40mm wide batten pocket stitched top and bottom and a batten all at a single point on the sail. Is this not an excessively 'hard' spot in an otherwise (relatively) flexible sail?

(as if modern laminate sails can be described as flexible )

I understand the principle of modern sail design with current cloths and the use of load paths, but looking at this F16 sail that 4th batten area just looks sort of disjointed and uncomfortable. The seams above and below the batten don't even quite line up?