Hey,
There is stuff made by Devcon called Liquid steel. The stuff is pretty amazing. You can get it at industrial stores. If you take some tape and put it over the bottom of the hole, you can goop it in and wait for it to dry. About an hour later just take a sanding wheel to it and you are ready to go. I have used it quite often and I swear it is almost as hard as steel. Plus, if you whack it with a hammer, it dents, doesn't shatter like a bondo type material. Good luck!