I have always cut the sails free from the jib booms because the stays never line up properly to match.

Jonas, wouldn't PLA plastic jib booms be sturdier and more resilient than resin, especially for rigging?

Rob, I use a pencil to draw in the sew lines on the sail. They showed through the watered down PVA pigment pretty well I think. The last 3 stay sails I made I forgot to do this so I lightly drew the lines after they dried. That turned out ok as well.