Put empty case in shell holder. Run ram all the way up. Screw die down until it makes contact with the case mouth. Back die off your desired amount. Set lock ring.
The OP's question IS, "what should his 'desired amount' be?" not how to set it. He knows that.
I'm a Forster seater guy myself, but I've been known to slum RCBS. The problem with all the ideas so far it that backing off the RCBS to prevent crimping does nothing to square up the die. You want the case/die/seating stem to be co-linear. The problem is that the case isn't really supported by the sides of the seating side, so there is slop. I like the square up this type of die with a flat washer, then set the lock ring.
That's a good suggestion to use a washer to press the die up hard into the threads before tightening down the lock ring. Here's a question - once you set and lock the ring the first time that way, can you just leave it locked and screw the dies out when done, and back in when ready to seat bullets again, without repeating the washer procedure, or must it be done every time?
I would also recommend the Hornady style lock rings. You can get them in six-packs to retrofit your dies.
Cheers,
Rex
