The amount of oil flow through the rocker shaft will be affected by the wear and clearance between the rockers and the bottom of the shaft. Doubling the size of the orfice at the rear cam bearing shouldn't reduce oil pressure enough to cause a problem unless there's an excessive amount of clearance there, and/or the other pressurized bearings such as main and rod bearings are also badly worn. Developing even one pound of pressure at the last bearing in the system indicates the oil pump is supplying more oil than the engine needs.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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