Just thinking out loud here but if you're still oiling the top end via the cam bearing the restriction isn't the rockers - it's something in the cam/cam bearing/timing area. Needles need less oil to operate, at least IMO. I will enlarge the passages and chamfer the holes in the cam, and chamfer the back of the cam bearing to allow more oil upstairs while still maintaining some control over the volume going up there.
Dave - if the pressure does not rise quickly and stay higher - mods or not - you have a problem. What are the clearances and oil pump/system you're running?
