JamieD said:
I also called Britax today but they were really no help :-( I didn't realize the Frontier had a wider base than the Boulevard and Marathon, though. I thought it was skinnier!
Yeah, I would describe the frontier as being "boxy" in shape. It is wide from top to base. The marathon (and similar-shaped seats) are also about as wide at their widest flared out area of the shell, but sit atop a more narrow base.
There is a great resource right on this forum. Find the heading "carseat features and data" and there are threads for each type of seat and it's basic measurements.
I know in my Prius 3-across, I have a ff radian drivers side, rf radian middle, and then I tried to fit a evenflo secure kid on the passenger side (a combination seat similar to, but more narrow than the frontier) and the door of the car wouldn't even close.
I think a third radian would fit, or a high back booster (our parkway SGL fits but has to be buckled by an adult), but I am assuming you need a harnessed seat.
A scenera is not more narrow than a radian, but might work as one of the seats. Maybe the complete air is narrow enough?
Also, how old/big is the rf child or the smaller ff child? If they are little enough, a Combi Cocorro might work for one or both of those children and it's really narrow.