That actually wouldn't be too difficult without 3DS Max...
1. Open up the decompiled GMF.
2. Find the object entitled "ball" and select the vertexes (lines 637 to 662 (inclusive)).
3. Copy and paste the data into excel.
4. At this point, the data should be separated by the tabs of the original code. Therefore, add a multiplier for
one of the X, Y, or Z columns (that will make a nice even egg shape of the spherical cannonball).
5. Then just copy and paste that new data back into the GMF. You may need to code the excel so that everything is next to each other.
I have an excel file that does this for me but its not at my fingertips at the moment (if I remember, I'll add it to this post later...)
Edit:
Here's what I use...
