The centre position is also the safest for baby.
I thought the same thing, but the ambulance guy when he fitted the capsule said that the side was safer because the base of the capsule/seat sits better on the seat. He said as a general rule the middle of the back seat is usually a bit raised and flatter so when the capsule or seat sits on it there is a little more play in it and has a slight rock. When the capsule or seat is fitted on the side it fits more snuggly into the seat. I must admit that in my mind for side impact that the centre is safer but is it if there is the rocking action in the base??

Kiki, that is what the ambulance also said that the safe n sound capsule is definitely the safest on the market for newborn babies.