I've seen a number of loads that don't work from BPI but I feel that it might be due to changing base wads heights from the manufacture. I use a lot of pickups from the trap fields and cut them to 2 1/2" for my shotgun and even hulls that look the same can be different.
In my drilling 2 1/2" 16ga I use 24gr of Longshot, Z-16 wad and 1 oz. of NPP BB's for my coyote loads and roll crimp them, it kills coyotes with authority.
For lead loads in an old 16 there is nothing wrong with 3/4 or 7/8 oz loads for hunting, my goto duck load is 3/4 oz of ITX #6 shot in the 16ga and 7/8 oz of the same in the 12ga all in 2 1/2" hulls. You can use a faster cleaner burning powder and keep the pressure down.
I would put the spacer in the bottom of the shotcup rather than over the powder.
Most of my drilling kills are withthe shogun barrels as I take it when the cover is thicker.