Bumgenius question

I'm looking to get some bumgenius, my baby is small and slim about 9lb10oz.

I know BTP diapers don't usually fit straight from birth so I was wondering what size the freetime and elemental diapers fit your babies?

I'm in am awkward spot where he's grown out his newborn ones and is too small for the pockets I have.

All in ones (in particular bumgenius) were my favourite newborn ones and because they are poppered you get much more use out of them. So thought I'd try some elementals