In some cases involving sphere-ball contact, its not the ball mounts but the frontmost hex bolt head that touches. This can be helped if not fixed by removing the hex bolts, countersinking the top plate of the sphere-ball, and using long 5/16-24 allen-flathead screws of proper length. The metric threads are very close to the SAE threads; if your are tight, a few run-throughs with lots of thread lube will convince the welded nuts and allen screws to play nice together. I did this to my Hall sphere-balls a LONG time ago and no problems since.
If the main body is also touching, a milling machine can cut the top/bottom surfaces to a minimum and give a little more clearance. The tops of the all-aluminum assemblies need not be perfectly parallel to the ground, either, but can be cut on a slant if that will help. There are quite a few variants of the Hall sphere-balls being sold today and I'm not familiar with any except the original Halls, which used a plastic body with a separate aluminum top cap.