ezwater wrote: If that worries you, scrape off the vinyl before using G-flex to glue directly to the ABS.
That's what I did when repairing the XL-13 I sold last year. The guy that bought it PM'ed me that he broke the thigh strap but the vinyl didn't come off when he pitoned it while creeking (if I remember the story correctly).
I use a hair drier to heat the patch and pull it off. The use of a chisel is a good one if you can guarantee that you want score the sub-straight or anything else like that.