Tom:

Some additional words about metal clevises. My preference in metal is the Sullivan clevis, with the metal locking clip.

But since the threads have clearance, allowing you to assemble them to the push rod, assuming the threaded ones, of course, that clearance will allow the two parts to vibrate, one to the other.

At best this will cause wear and increased looseness, eventually failing. At worst it can cause RFI and radio failure before it comes apart from wear. Either can cause destruction of the plane.

So if they are so bad, why are they so popular? Simple. People have learned how to prevent/eliminate the looseness.

1) Strong LockTite, the red, not the blue.
2) Run CA into the threads after adjustment.
3) Use a locking nut as BillHarris said. Sullivan also supplies very small brass locknuts in 2-56 thread, I think they also have them in 4-40.

My method, akin to belt and suspenders, is the lock nut AND CA. Never had one come loose. Or wear the threads.

Bill.