I'd say 1"-3" is pretty good size and they should overwinter OK.

I know it's against popular belief to feed fish when water gets below a certain temp but I know some people who do. Apparently they think fish know when to eat and when not to eat. Something they learned before people controlled the food.

The only time I had trouble feeding my fish was in the spring. They ate it up but couldn't digest it, so they got brought inside where things "worked their way out."

One fish swam around butt end up for 3 days due to intestinal gas. I made them some special food which may have helped, but didn't loose anyone.