Been driving the Y for a few years now and honestly, its been a dream for kids. If you're looking for that slim profile to save room for other passengers, I'm super happy with the Diono Radian 3RXT All-in-One Convertible Car Seat. They are heavy but they fit like a glove in the back seat. For rear-facing, the Graco Extend2Fit Convertible Car Seat is actually pretty decent because the Model Y has surprisingly good legroom, though it can be a bit of a squeeze if you're tall and have it right behind the drivers seat. If you have an infant, the UPPAbaby MESA V2 Infant Car Seat is what we used and the LATCH system made it a breeze to click in and out. For the older kids, Tesla is spot on with the Peg Perego Viaggio Shuttle Plus 120 recommendation, it fits the seat contour perfectly and doesnt rattle. Honestly just take your time with the top tether because the headrests can be a bit funky to work around... but once its in, you're golden. Let me know if you need help with the install steps!