We have the Unity for that very reason. DD is already 7kgs and it goes up to 12. The first time you fit it, it is a bit awkward, but once you get the hang of it I think it is worth it, given that they will be able to stay in it longer. Having said all of that, I know a couple of people that moved their bubs straight into the pram seat at around 4 months (in the fully reclined position). I know they say not to, but I have seen young bubs in the seat and it looks fine to me. You are welcome to come and check out how it all works. I can give you a demo haha!