measure your concentricity and see what it does on target before you give up on it. i'm liking the SAC bushing I have, wouldn't mind having the .289 and .290 to do a bit more experimentation.
Also, there's at least one theory that bullets don't get pushed out of the neck because of force on the bullet base, but rather released from the neck because the pressure that swells the case body/shoulder also causes the neck to swell. IF that is true (and I don't know that it is), then the amount of the neck that is sized is entirely irrelevant. For at least an era in benchrest shooting, sizing only part of the neck was common practice in benchrest. the theory was that the unsized portion of the neck would contact the chamber and help improve the alignment.