Stats: 18 months old, about 31" tall, nearly 26 lbs naked weight, more torso than leg but she's starting to even out.
Car: '05 Honda Civic. There's a Coccoro installed in the center. That is a super duper challenging car for 3-across, and there's not a lot of front-to-back space either.
It was cold and raining but I would have liked to have played with it a little longer for fit. Maybe Judi can chime in because she had a better viewpoint than I did overall.
The verdict: When the RF Coccoro is installed in the center, the Foonf fits
like a glove on the seat FF (seat belt install). The only hitch is the door handle which will hit the Foonf slightly if you aren't careful about scooting everything over. It would have been interesting to try putting another Foonf on the other side to see if it still fit.
It's a little tougher with the Foonf RF. The Foonf can be installed RF in a couple of different modes, fully reclined or fully upright.
When it's upright, there is no anti-rebound bar. With the CCO installed in the center, the Foonf does not fit RF. Width-wise, it's fine, but the edge of the vehicle seat curves forward so sharply that the foot of the car seat does not contact the back of the seat except on the very outside corner. I am positive there would be no issue if I didn't have another car seat installed in the center. It also might work if I were to swap and put the Foonf in the center and the CCO outboard, but we didn't try it (and the height of the Foonf might be an issue in the center anyway because there's a pretty big hump). When it's reclined, you use the anti-rebound bar.
With the anti-rebound bar, in the reclined position, it is a tight fit, but it fits (and the door doesn't even come close to hitting it!!). The Rebound bar almost contacts the full vehicle seat back when you set it in, and if you tighten it down (which we didn't do) it should make full contact and be stable. The problem there is that it takes up more front to back space with the rebound bar. I'm going to need to play with it more in the future to see whether there's a happy medium which will allow sufficient/safe front seat space AND the reclined position with the bar.
By the way, a slight change has been made to the Foonf usage instructions; when it's upright (toddler mode, over a year old if I understand correctly; I was off chasing my tot when he was explaining all that) and the anti-rebound bar isn't in use, it can be rear-tethered.
So you basically have options whether you use the ARB bar or the RF tether depending on your circumstances.