When I have to pick up my Runners I am amazed at how light they are. Especially my drake Snoop, But that is just the way they are thin and upright. If Limpy is eating good but still struggling you may want to make a smaller area for him like we talked about before especially over winter so the feed he does eat isn't run off so fast. he is def going to need some special attention. Trying to keep up with every one he isn't keeping enough reserves to help him and cold weather may take it's toll. I know it will be rough for him not to be able to run around with everyone but you could rotate the others in with him so he isn't lonely, but it maybe the only way to get him through the cold weather.