+1 on drilling a small 'stop' hole at the end of your crack
I used fiber glass on my Ninja lowers a couple of years ago and the repairs have held up, so I used fiberglass to repair about 16 holes in my VR top box and the 16 holes for those four silly little bags. In addition I had the rebuild a tab on the main fairing. I 'stop-drilled' and fiber glassed a couple of cracks in the top box and one of the saddlebags.
So far, so good