Line that is too thin will be hard on your or your crew's hands. If you're going to be trimming this sheet a lot, get something that's comfortable to hold. Stretch makes a big difference in a sail like this. Imagine a puff filling the sail and the sheet stretches. The sail won't be trimmed properly any more because the line has stretched. Because the sheet has stretched the sail first luffs and then collapses. You head
off to get the sail filled, and it does, making the line stretch more, so you trim it in. Then another puff hits and you do the same thing all over again. Stretchy line introduces an extra variable that is not helpful for relaxed sailing. We race
, so our spinnaker sheets are Spectra with polyester covers. You don't have to go that crazy, but less stretch and comfortable to use are good things.