I shot mine both ways, at 550 and 850psi (Ninja tank with shims in and shims out) I do not find any difference. In both cases, I get +/- 3fps. It is really consistent.
Now I have not shot mine much, so I can not speak to the excessive wear, I have never blown an O-ring.
If you are using a Ninja tank regulator, you can adjust the pressure by removing the shims and run you T2 and AC at 550psi. You will get a few extra shots out of a tank and it will not reduce the performance.
If you decide to run your 17ci tank at 550psi and want to run your other markers at the lower pressure, don't forget to re-adjust your regulator pressure on your other markers. If you reduce the input pressure by 300psi, your in-line regulator output pressure will drop 35-40 psi.
Good luck and you can PM me if you want more information. See you soon.
"This is the weapon of a Jedi Knight. Not as clumsy or random as a blaster; an elegant weapon for a more civilized age." Obi-Wan, while showing A CCM to Luke.
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