Redding and other’s instructions are for novices that it doesnt matter to if they push their shoulders back .015 or .030 as long as it goes off in their guns. No accuracy minded shooter that i know of just blindly screws their dies down to the shellholder and starts loading. Custom dies are shorter for a reason. That reason is so that the press or shellholder does not influence the case going into the die such that it will if you touch the shellholder. You have to remember the audience they have with die instructions. There has to be a fail safe built in so that the average reloader doesnt push their shoulder back .100
I'm 68 years old and have been reloading for over 47 years and also know that chambers and dies vary in size. And the RCBS die instructions are to insure the full length resized case will chamber in any rifle regardless of the head clearance.
So to keep this simple Redding made the five competition shell holders so the die could contact the shell holder and square the die.
And we are talking about the best lock rings, so I guess you can say my question is how do you know the die is square and not tilted in the press threads if it is not touching the shell holder. And how do you set the die and its lock ring up to make sure the die is square.
Again I'm going back to the 1974 Speer manual and the chapter on setting up your dies. Do you shim the die with a feeler gauge between the die and shell holder to square the die and then remove the feeler gauge.

Bottom line how do you setup your dies to remove the slop in the threads with dies that do not touch the shell holder. And how do you know when you tighten down the lock ring that the die is square and not tilted.
This posting boils down to your favorite lock ring and how you like to secure the lock ring. But I'm asking regardless of the type lock ring what do do to ensure the die is centered and square in the press "before" securing the lock ring.