Thanks Mike - all excellent and helpful points to keep in mind. The intended use here is sporting clays. The gun in question currently patterns my reloads at 91% at 30 yds (R) and 84% at 40 yds (L). Based on the principles you discuss, I am concerned that the Polywad insert may not produce a pattern that would still be useful at longer ranges (30+ yards) - though the only way to confirm that is to load and pattern.

Such a long, long time to be gone, and a short time to be there.