My DD is now 5.2kg and still doesn't fit all her OSFM nappies. Cushie Tushies have leg gape to the point where I'm putting them away till she's bigger (though I love the patterns!). She has a Baby Beehinds Magicall Multi-fit (pocket) which always leaks, but her BBH hemp fitted and small Magicall AIO are fine. Of the pockets, Tots Bots are good, Pixie Poppits are good, Haute Pockets and Happy Heinys are ok but wide. She's been in Itti Bitti smalls since birth (weight 3.3kg), and from the second month (3.8kg) in Jamtots Berryplush - they're both snap-ins, and work really well. ATM I'm really liking Imse Vimse small AIOs (leg gussets for poosplosion containment!) but I don't know if she wouldn't have fit them earlier as only got them a few weeks ago (small = 5-8kg in their system).
We did flats and covers as a newborn too. Once you get used to folding, it's not such a big deal, and Snappis make the fastening process much easier. Covers are excellent for containing nb poo, and this is by far the cheapest way to do cloth.
As of 2 weeks ago her measurements were waist 38cm, thigh 20cm, rise 26cm - I'm not sure if that makes her skinny thighed or waisted or what. Has anyone ever put together a chart for matching relative measurements to appropriate nappy brands? That would be really useful...