I have the Graco Affix Safety Surround Side Impact Protection Highback Booster. My child is 9 years old, 51" tall, and 65 lbs. She does not meet the maximum limits yet. However, her shoulders touch the side-impact pads next to her head, even though we have the back on the highest setting. Does that mean she has outgrown the booster even though she isn't near the height and weight maximum limits? Do we now transition to a backless booster? Thanks.