New seats are designed for high speed impacts, god forbid it never happens. There also designed to keep the child in a certain position. There MIGHT be a guage level thing that you need to put the seat in so this gauge reads a certain way.
Suzuki desinged the back seats, I think anyways, with child seats in mind so chances are no modification of the seat base level thing will be needed. Read the instructions twice and take the seat, minus child, to your local police department to be inspected. My boy is 2 months old and his first ride was in an XL7 with LATCH... LATCH is AWSOME compared to the belt method we had to use on my wife's lexus (which is NOT child seat friendly what so ever).
Also sit on the seat when installing it to compress the cushion. There's some video's on-line that show the proper way to do it, run a search for "Child seat installation video" and they'll pop up.