[Minnewaska]

I would fill with thickened epoxy and redrill a small pilot hole, at the least. The old screw grooves should hold the plug. If wet inside, I would first overdrill the existing hole, by only about a 16th inch, and then dig out some of the core to create a groove to hold the epoxy plug.

I too like twist fasteners better. While a much larger project, you could buy the kit to replace the snaps on your canvas, with grommets. The dual screw twist fasteners would not require the original hole at all.