If you are loading your own shells and are going to "blend" the shot size, which load would go in first (closest to the primer)?
I'm thinking about loading some 7x9's but don't know which to put in first.
I have not done it but I think that you put the 9's in before the 7's so the 7's don't blow through the 9's in flight.
If both sizes are of the same material, you put the smaller size on bottom. It gets a bit more complicated if you are duplexing different sizes as well as materials, e.g. TSS 9s and HS 6s.
Heavier shot on the top as the other guys have said. My educated guess is that you will probably like the straight 9s better than the duplex. I've tinkered with different combos and always go back to the straight pixie dust. Wayyyyyy more than enough to kill them at the forum's max range. Let us know how you do. Good luck