I realize this post is old as hell but I'm going to reply anyways. I had a similar hole that I took a half dollar and some JB Weld to and patched it. I know it's red neck as it gets but it held and didnt leak. Clean the area best you can, not getting any dirt in the case and let the JB set up some before putting it on the half dollar and on you case because it tends to want to run and you want to use as much as you can on the exterior ( outside ) of the hole as you can not letting it run inside or down the side of the case. Let it set up some!..... hope this finds someone and helps.
use this method at your own risk...results vary depending on size of hole and your head......