Current Projects chat and miscellany

My suggestion: drill a second hole a little above the first. Find some plastic pipe with about the same diameter as the chainstay bridge, cut a length to fit the gap. Loop a cable tie around the chainstay, through the pipe, through the old and new holes in the guard, and back through the pipe.

This, except Moth, did you mean to loop the cable tie around the bridge instead of the chainstay?
Also, instead of a second hole in the fender, you could shape aluminum into a dog bone shape, place it between the fender and tire and then loop the cable tire around the narrow part of the aluminum piece before sending it back through the same fender hole.