Hello, I have had a problem for a while. I have spent time in the car seat section at several stores. My daughter has a disease that makes her gain weight at a different pace than children her age. She is 4 and 60lbs. The harness fits her chest but her thighs are the problem. I can not get the bottom to connect without straining and hurting her. She currently has a high back booster, we use the cars seat beat to strap her down. Is this my only option? I have a hard time swallowing just having her in a seat belt strap. Her teacher said just a booster but I don't think I want just a booster.