DH and I were discussing this the other day when reading all the advertisments in the paper for the new laws. In some cars it will not be possible to safely have 3 car seats because of the size of the seats in the car. In our commodore sedan we could just get two s'n's boosters plus a s'n's comvertible car seat across the back, but you did have to slide the boosters out a bit to access the buckle to do the seat belt up and then slide them back into place. It wasn't much you had to move them though, maybe and inch or two. I assume the royale will be used for the baby? Maybe have a look at what smaller, compact seats you can get for J as I know they do make some for use in small cars and they have a smaller base width.