I know a few people were curious to know how a rearfacing child carseat would fit in the second row of the Model X. I tried both of our convertible car seats and they both fit. We have a Clek Foonf as our main car seat and a Cosco Scenera NEXT as our travel car seat. The Clek took up much more space because it is huge, but it still fit and the front seat was comfortable for me (I'm a 5'6" woman). I'm not sure if it would fit comfortable behind a 6'2" driver. The Cosco Scenera NEXT had much more space and was more comfortable for the person sitting in the front seat with the car seat behind them, but that makes sense since it is a relatively tiny car seat. I could not access the third row with the Clek Foonf, but I could climb back into the third row with the Cosco Scenera NEXT. It wasn't as easy as it is normally, but it could be done in a pinch, especially if kids are the ones climbing back there. Attached are some pictures in case that helps anyone. Image 9793 is the Cosco Scenera NEXT, image 9800 is the Clek Foonf. Also attaching some pics of my travel stroller in the car, since people looking for info on car seats are probably looking for info on strollers as well! The stroller is a Valco Snap - it's a little bit smaller than a City Mini stroller.