Didn't realize anyone had found this blog.
Sorry to say, I took the sling to a few places to see if they could re-do it. they all agreed that they could sew a fabric cover, but they don't have the stiff plastic/resin strip that fits into the channels on the sides of the chair and they don't have whatever very strong and resilient interfacing goes on the inside of the sling to prevent it from stretching and deforming after a little use. Most Upholstery fabrics are supported by foam on the inside so the upholstery itself just contains the support system. On the aluminum group chairs the fabric sling is the support system itself so ordinary fabrics won't work.
I probably gave up too easily, but my GF wanted it done or out of the kitchen and I wasn't getting anywhere. So it went back to the curb. If anyone figures out how to make a new sling that works, let me know. I see these cheap from time to time and I'm dying to take another shot at it.
Sorry to be a disappointment.
