I have done all 3 of mine. I don't remember the exact size I went with, but it was a middle of the road one. Most of my use is between 4000-7500, with up to 9500 occasionally.
So I picked a size that covered most situations. I know I am still a little rich at 9500.
The fuel usage and power output is slightly improved over stock. Not a lot, but it is noticeable. Yes I have done a side by side comparison, before rejetting the last two.
The big payoff is likely long term. The spark plug and combustion chamber should be likeing the correct A/F mixture a lot.
