If the OP "512" has a fresh build and it was pushing well above 10 PSI before he yanked the Slider cam and put in this roller cam and lifters and now he has "15-18 psi at (850 RPM) idle while in gear. 10W-40 Dino oil", he is above that 10 PSI @ 1,000 RPM.
I do not know if he posted his pressure at 1,000 RPM, could be it is well above the 18 PSI at 850 RPM, but speculation here. ASSuMe.
He is oiling the rockers thru the roller lifters and pushrods so, not much if any PRESSURE at the fulcrum of the rocker. Pushing more pressure to the rockers will not help, BUT more volume may.
You guys will argue about Buttermilk in the dinner rolls for tonight's dinner.