Thanks for the responses! I was already leaning toward the 16, pretty sure now that's what I'll go with. I'll play with loads as a cylinder bore, if I can't get it where I want it I'll look at having some choke put on it. Good pattern out to 30 yds is all I need. Heck, it's so thick around here I've had birds gobbling at 15 yds and have never seen them.
The comments about 10 and 12 bores are interesting, but the 16 just seems to have the lightest weight and frame size I want to build.
Geese would really be an afterthought. Got a 10 sxs cap gun I bought for waterfowl years ago, but barely use it. Just such a pain in the boat and blind and around all the saltwater. Taken a few with it, but hard to get fast followup shots on crips, too. Especially divers.
This one won't get steel in it. But, well, ya know, if it's loaded, and the geese get off the field in the morning and fly over the house, and I happen to be standing on the back step, well, things happen.