My carseat (infant reversible) says cannot be installed in a hatchback with a split rear seatback as the straps can fall down the split, rendering it unsafe... We've got a Getz hatchback with a third/two thirds split, so we just put the seat on the side with more back, and it's far enough away from the split that it's not an issue. We did need a tether extension to get it to reach to the anchor point in the boot though.