What size shot are you using, Pat?
From my own experience, I'd say steel #4's are about the minimum for consistently clean kills on decoyed ducks, excepting teal where a smaller shot size can be used effectively if the birds are being taken close.
Stan & others are giving you sound advice about using more shot for better results.
When you look at the larger picture, inclusive of effort and overall cost to hunt ducks, it makes no sense to let the high cost of non-toxic shot become a deal beaker. I realize you are seeking a lower pressure solution, but it sounds like you are also loading 'blind' & that is not the best approach. Call BP or check with Alliant about the exact wad & primer to be using w/your shot & powder and keeping the pressures at a low or reasonable level. Both normally have more tested data than they publish.
