Dragonbub (love your screen name BTW), I think you are on the right track not buying 00000s. My DD was premmie (35 1/2 weeks). She weighed 2.485 kg and was 47.5cm long. She had one 00000 bodysuit, which she wore for about 6 weeks. Otherwise, she was in 0000s pretty much from the start. They swam on her for a few weeks, but not too badly. She is still wearing most of them now at 10 weeks, except for the suits and trousers with feet, which she outgrew at about 8-9 weeks. When she outgrew the footed suits, I started putting her in 000s, which are still a bit big but fit reasonably well now.