Fitting multiple kids (with car seats!) into a small car

We can't be the only ones with a compact car who have wondered how on earth you can keep your small wheels and potentially transport 3 kids around. Car seats just seem so big. So far we've been very fortunate with our setup. Two Britax Roundabouts in a Honda Civic. With twins anything bigger, like the Marathon, just wasn't an option because we couldn't fit them in rear facing. We are still able to use the middle back seat to squeeze in one small adult - and often do - but I've wondered what would happen if we needed to get another car seat back there. Or even to make it comfortable for the adult back there.

I just learned about this Radian Car Seat line which I would have opted for in a SECOND over our Roundabouts if I'd known about them when we were buying. They're each about 1.25 inches narrower than the Roundabouts but add it up and that's 2.5 inches less car seat which in a compact car's back seat is significant. An added bonus of the Radian seats is that the bottom folds up into the back for really easy travel. They're supposed to have a great safety record too. Oh, and the sides aren't as high as the Roundabout's. Initially that seems like a nice comfort feature but it makes it difficult to maneuver the girls into their seats given the car's low headroom and if they squirm I often end up accidentally bonking them while getting them in their seats. Poor girlios!

And I just want to put in a plug for making due with a small car and twins. At first I was worried with the strollers and gear we'd be squeezed too tight. I don't rule out getting a second bigger car when we do more carpooling and traveling around with their friends but for now this is perfect.