I can't speak for how it sets under sail or for durability yet, but I can recommend the affordability of used dacron/terylene polyester. I bought two used genoas for about $50 each and cut them up to make my panels total 30sqm. It's not very elastic (yet probably a lot more so than new), so it might be better for flat panels or boom-shelf camber, I sewed in a barrell camber so I'm expecting a lot of wrinkles. We'll see. I think the original sails were 1980s vintage, so I'm not sure how durable they will be but I can't tear them that easily. I'm sure they will be good for my experiment, I am not going offshore.
They aren't fancy coloured but they're not white anymore either, kind of stained grey ivory. I'm curious to try some colouring options in the future. Maybe some pattern design impressions with a rusty chain, and I've heard that diluted wash of outdoor latex paint can work on dacron. Again, we'll see.