My son is outgrowing his Britax child seat and needs a belt positioning booster now. I went out and picked up one from Cosco - the Protek. However, the manual states that the back of the booster's headrest must be supported by the back of the car's seat. I checked out the Graco one - same thing! The XJ's have a very low back seat. What do you do? My son is too small to sit on just a plain booster, so he needs one of these belt postioning ones. I either need to add support to the seat, or find a booster that will work with a low back seat.