We are going to put one on each side.

I'm just not sure which one yet. I will probably put the car capsule on the right, because i would rather me be on the road then getting DS out on the road.

With our car (Nissan Pulsar) i don't think i have much choice. With DS currently in the middle it impinges on each of the other seats, so i don't really feel that i can put them next to each other. But i can't for see anyone sitting there anyway (cos for us 2 car seats/capsules really takes up 2.5 seats), and if i needed to put somebody in the back i could always move a car seat across (which only takes a few mins anyway).

And also this way i avoid DS touching/hitting/doing whatever to the baby.