I have two slings - an ergo and bjorn classic
My dd is 10 weeks and weighs 5.5kg - she is long 60cm
My bjorn is already killing my shoulders with a rucksack on too but I din't have the newborn insert for the ergo. Is there any way of using it without buying one - dd us alert and has good neck control already so I think she might not like the insert so don't want to waste money. Please.