My girls were 1.8kg and 2.0kg. I found the trimmest were Very Baby XS, Kissaluvs size 0 and Swaddlebees NBOV. They were all great. Bubblebubs sherpies were also good as were Raphaels. I also had some Peenuts fitteds that were passed onto me and were a fantastic fit (I don't think you can buy them now).
For covers, I loved Bummis SWW in NB and ME Rikki in XS.
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Big sister born November 2005
And twin pink bundles born October 2007