Spot weld is about the best way to go at it. If you need to swap to different size, just slide in another and make sure that one is spot welded too.
Wannabe...
Wannabe...v2.0
A lot like the old Wannabe... except with fewer bad words. And Karate chop action. But, yes, still purtier than you.
I have a lock on my trailer and one on my reciever. Now after reading all of these post I am going to have to drag out my mig welder and weld my ball. I have about three recievers so I can leave the ball on for a quick change of ball size.