full groove main bearings oil pressure ?

Now your last paragraph on opening up the oil holes and the bearings being able to handle the extra flow is diving way too deep. The oil flow for the main, rod, and cam bearings is limited by the radial clearance. If you increase your radial clearance to try to get more oil flow through, the clearances will be too great. The engine will knock due to the excessive clearances and you will wipe out your bearings and mating components

I never said anything about " If you increase your radial clearance to try to get more oil flow through" I was talking about cleaning casting flash out of the cast in oil passages! The bearing clearance provides a "calibrated leak" if it is to large you will not have good oil pressure. Yes you can have excessive oil to the valve train.