Sasa, my DD is 11kg too, and fits on the middle snaps of the medium. She is a short child for her age, but i'm starting to think, it's not so much about the kids being short or tall, more to the point, it's what's their RISE is that is so crucial to the nappy fit.

other narrow crotch nappies we use:

AI2's
dragonflymagik (minky with hidden PUL)
lotus (shut at the moment)

pockets
beetlebums (you need to be a hyena)
swaddlebees sized with organic velour inner
sugarshots

fitteds
cute tooshies bamboo delights
whizz kidz (shut at the moment)
daisy doodles (bamboo velour)
swaddlebees fitted pockets with Organic velour inner
swaddlebees organic velour fitteds (inner AND outer)
very baby (at the weewuns)

night nappies
dragonflymagik (hyena a custom)
kester kovers aio (at possum's pouch) they do a medium long size
whizz kidz (shut)
lotus (shut)


itti bitti do narrow crotch too, their site recommends you getting the next size up if your child needs the rise (they are a low rise nappy).
the itti bitti boo - fitted nappy
the itti bitti dlish - ai2