I have to admit to having shot 3 1/4-1 1/8-8 loads at doves for many years as a young man. I was not a "questioner" then .... If it worked I used it and didn't wonder why. As I grew older I became more inquisitive, and eventually wanted to know just what was necessary for different kinds of dove shooting. Today, I use everything from a 1/2 oz. .410 load, in the early season, to 1 oz. with tight chokes, in the late season. But, I can honestly say I do not believe there is any sporting circumstance where more than 1 oz. is needed to bring down a dove, even a very long, high bird. If you can't kill him cleanly with 1 oz. 7 1/2s, and a full choke, he probably should be given a pass, IMHO.
I was mostly kidding you, tho', because most of my dove shooting buddies use 1 1/8 oz. religiously, all season. (Doesn't make it right, tho'.)

SRH