Fixing egg shaped holes in masthead

[Brion Toss]

Hello,
I hate it when people do that, but it is usually fixable. First, we need to be sure that the masthead isn't deeply damaged; sometimes the aluminum can get fatigued in the way of the point-loading, even beyond the area that might get reamed away for the fix. Next, tell me how far the egg traveled, and what size the hole was originally. In other words, how big a hole will you need to ream in order to get to fresh metal.
Finally, how far is it from the edge of the hoped-for enlarged hole to the edge of the masthead, and how thick is the masthead metal? We are hoping that, even after some metal has been removed, that you will still have an appropriate amount of meat left.
Pictures or sketches would be nice, but not mandatory.
Fair leads,
Brion Toss