I took care of some chicks at a Fall Festival last October. They were all mixed bantams from MM but one was as you describe...wa-ay tinier than the rest (hence the name Tiny). The farm didn't have any place I could put him/her separately, so I just kept a very close eye on him. I saw that no one picked on him and that he was able to eat and drink whenever he felt like it. He snuggled up with the rest to sleep. But oooh, was he TINY! When the festival ended, the chicks were about 8 weeks old and Tiny had caught up to the point that he wasn't ridiculously undersized anymore although he was still smaller than the rest. In his case, I think it was best he stayed with the others as he got along okay and he had friends to hang out. You might try putting yours in with the rest and just watch real closely that they don't pick on him and he can eat and drink. Just a suggestion. I hope he makes it, whatever you decide to do!!!