I have a "vsc" style gauged phantom with a male stab (in place of the bucket changer) going to a bottom line air tank. Stock hardlines between valve and vertical ASA and between stab and bottomline ASA.
I have stock springs, SSC lightened bolt, open-face TPC. 12" Deadly Wind Fibur Barrel, tymcneer brass inserts. My gun runs between 550 and 800 psi depending upon where the TPC is set and I generally try to shoot between 285 and 300FPS(field limit). Typically the TPC is usually set to its lowest spring pressure settings.
When adjusting the reg I find that increasing the preasure beyond 550 psi decreases the FPS, and sometimes it is only by decreasing PSI that I can achieve playable velocities.