For the curious, my girl's currently about 6.3 lbs. She's 11"x11" in length and height at base of neck to rump and back to floor. 13" girth at the thickest midsection. All four of these outfits are sized at SMALL. She also fits MD snowsuits at size Medium but it's a little loose on her but I would think SMALL would have been too small for that, but for the ones pictured above, it seems to be right. I would guess that XS would be too short if not too snug too. This will leave room for more hair come winter and perhaps an undershirt.
By the way, for Canadian buyers, she's great for shipping rates.
