That detailed A MAY be moving close to AA water volume. Personally, I'd cut the A, BUT, you can never go back. I'd have to be certain I was not going to mind the holeshot pulling loss of the cut, and want the RPM. If there's any chance of you going back, buy a "B", you could have it detailed later, BUT, you will probably need to re-do the wear ring clearances for it. That would leave you 2 setups (impeller, ring, shims).