I ran undrilled bronze bushings on the street w/ solid flat-tappet lifters and saw definite wear patterns and extra clearance in the bushings. The late Dan Costello lent me a fixture to add holes to them, so I added .125" holes before I switched to solid roller lifters.

Everyone who hears the size of those holes always acts shocked and tells me they're way too big. Well, they're a He11uva lot smaller than the size of the galley opening in an unbushed lifter bore, and the engine had no oil pressure issues on the dyno either at idle or WOT up to 7200 RPM.