gunnertom, once you are breaking 23, 24, 25 almost all the time, shot size might have reason to drift into your mind. Until then, it's just one more thing to get diverted by and make some unsupported decisions about.*
Shoot lights. That 2 3/4 "dram equivalent" or under 1150 ft/sec if you shoot 1 1/8 oz. loads. If one ounce, and there's no reason not to, then a little faster is OK. But not much faster or you are not getting what you are after, reduced recoil.
Just buy any light shells.
Neil
* So what's wrong with a few unsupported decisions, you ask? Well, say you begin to suspect that 8's are "best." And then have to shoot something else and miss an extra bird or two. You will be inclined to tell yourself "It must have been the shells." It wasn't; it was you, and you've passed up a chance to look hard to see what it _really_ was. Mostly, it's just chance anyway, but even that is _well_ worth knowing, probably more worth knowing than what's the best shot size, if any.