Claus,

I would have taped all of them, as long as they are in the spi cloth and not the edge tapes.
Abrasion while snuffing might be a problem with the patch close to the retrieval point, but I would try without stitching first. I am too lazy to take out the sewing machine without really needing to.

How long do you expect to have/use this spi? The spi is the first sail to wear out on our boat. It's performance life is just so much shorter than it's mechanical life.