I believe the Mr. V.M. Starr, one of the best bp shot gunners ever, insisted on using only the absolute minimum wads. His load consisted only of equal volumes of powder and shot. Loaded in the following manner: powder, o/p wad, shot, o/s wad. His wads were all the same.. He stated that any other wads were a waste of time and materials. Might be worth a try.
Jim