I have a 7 month old who has long legs. She is in a Chicco Keyfit that says it can be used until the child is 30 inches. She is almost 30 inches but is not close to the top of the car seat (there is another strap location above her shoulders). Should I move her into a Convertible seat when she reaches 30 inches even though her upper body is several inches from the top of the seat? If so, this goes against what the manufacturer says. I am more concerned about having her in the safest seat than the fact that her feet may be bent.