Proper nylocks in the proper application work very well. El-Cheapo nylocks will die quickly (and show great distress when installed). Nylocks in a hot enviromment (near exhaust, on head or manifolds) will also die quickly. Also, nylocks are a one-use item for maximum holding power.

Try cutting a slot for a flat screwdriver in the end of the stud on the ball. Then you can hold it while tightening the nut. I have never had an issue. Perhaps if you lightly tap the stud into the arm from the back (ball-side) it will develop enough friction to hold it for you?

Mike!