I've shoot ATA with only 16's. I also shoot games weekly in the summer many times 3 to 4 days a week
On ata handicap I seem to be stuck on the 25 line. But this summer I shot very little ata.
I'm more into the games. I can usually pay for my fees of the games . On shootoffs I have never felt handicap. At what is called back fence, parking lot or where ever shootoff is. Generally 15 to 40 yards behind the 27 yard post. I use the same load all the way thru 16yrd to shootoffs and i keeps up with any 12's. I've switched from my mod 12 16ga full 28" to my 525 citori 32" Muller cks about 3 years ago