Same thing has happened to mine. I am hoping to get them repaired before we leave as the shop deals with an upholstery shop that does a lot of RV work. I think there is a nylon type thread available that will resist UV damage. Florida Golf Cart's Tim has a brother in Titusville that does upholstery. He has moved from Hopkins St but might still be in the area. He did a small job for me on our old Tracker and was quite reasonable at the time.
The hardest part will be getting the fabric off the Aluminum cover. The rail is crimped at both ends and damage to the fabric is quite possible. Roy, the Service Manager at work, told me to remove the whole assembly and then take it to the upholstery shop. They should have an easy way to remove the fabric. I need to get the coach over there this week and have them look at it again.