Cap Assembly w/ Adjusting Ring - 1H Kitchen in Chrome

My kicten handle is leaking and I what to replace the RP50. I can't remove by hand I believe that it's been over tighten. So is there a tool that can be used to loosen it with to much damage to the finish?

I have a Delta M/N 100 single handle kitchen faucet that has a P/N RP50 cap with a plastic adjustment ring (rather than the P/N RP 1050 cap). The spanner portion of the Delta tool is made to use to adjust this plastic adjustment ring. This plastic adjustment ring will vary the compressive force between the ball (P/N RP70) and the seat springs (P/N RP4993) as well as vary the amount of "reveal" of the seats outside of the stationary valve body interior (where the seats meet the ball). My previous efforts to adjust this ring seem to have resulted in either too little or too much compressive force being exerted between the seal/springs and the ball which seems to have significantly reduced the service life of the seals. Exactly what is the proper procedure for making this adjustment? Any help you can provide me on this adjustment procedure would be greatly appreciated.