Hello Jello,
I generally have used 4 Common Eider and 8 Old Squaw decoys or 4 Golden Eye and 8 Canvasback decoys when I hunted "divers" on Lake Ontario at Presqu'ile Provincial Park. A few times I combined both "diver" sets with a few mallards as well with no better results.
I generally have used just 12 Mallard (including 4 tippers) decoys when hunting within the LPWMU since 2004 as I have been hunting blinds 5, 6, 7, 20, 21, 38, 39, 40 and 41 only. I have shot a few "divers" at blinds 6 and 7.
I started hunting "divers" north of Big Creek (outside of the unit) this year ... Redheads and Buffleheads so far.
I hope to have my "big boat" operational by next fall.
Jerome