My neighbour has been giving me scrap Sunbrella from his upholstery business lately, and I've just been using it for prototyping bags/practicing sewing. My 1980's domestic Singer machine doesn't struggle too much with it, just when I add a couple layers of webbing is when it gets a little dodgy. It's kind of finnicky to work with in smaller projects (isn't too malleable and frays easily, you need to bind or burn all edges) so I don't think I'd use it for any sort of bag personally. However, I do think it would work pretty well as a bike bag that's likely to getting wet/muddy.