I use .020" patches only with bore sized balls or larger. All balls that are smaller than bore size, even .001' smaller, gets thicker patching- .0215" ticking or .0225" denim to the even heavier mattress ticking. That's about all I can think of, Herb, other than consistancy. The larger sizes do give closer variations. For me, 2f gives closer velocities strings than 3F.