Is that mixed shot sizes?
If so there is no advatage at all to mixing shot sizes.
Several gun writers have tested patterns with mixed shot & found no
difference between patterns with mixed shot sizes & the same recipie
with one shot size, all other components being equal.
Francis E. Sell debunked that notion years ago.
Sell was the foremost shotgun load & reload expert in his day.
Sell was experimenting with plated shot, buffered loads, years before the industry
started producing buffered shot shells.
No doubt Hevy-Shot loads pattern well due to the heavier than lead & the
hardness of the shot pellets.
I've patterned it & it's very effiecent & should make a great
waterfowl load.
Lots of hunters around here use it for coyotes.