I have a 10 yo 62 lb with a seated torso height of 19". She is on the autism spectrum, has heart problems, sensory issues and more. Her therapists have said she has low muscle tone but i honestly dont see it. She can just, stand, walk and do just about everything else she wants to fine. She has a Britax frontier that she has outgrown the harness in. She has ridden in booseter mode for short trips and did OK but simply isn't 100% trustworthy in a booster on a regular basis or for long trips. Extra supervision and lots of threats of you will have to ride in your other seat keep her sitting safely in a booster for short trips. I have a Monterey booster that isn't being used right now that she can go into, I can booster mode the frontier, or get her a special needs seat with a harness. Insurance will cover a sn seat so no issues there. But my question is all around which is the safest option? Assuming I had any hope of training her to sit properly in a booster all the time? I think I've read where you loose safety features on the sn seats. Things like the head wings that both the Monterey and frontier have. Not sure this is true though. From strictly a which seat is safer view which of the three would be the safest option? From the view of my daughter has special needs which seat becomes safest? I also have the option of buying the frontier 90 but she would only have 1" of growing room. Also, is there any hope of getting a 3 across in the 3rd row of a 2004 Chevy venture with a special needs seat? I can get three across the third row with the frontier, radian xtsl, and Monterey. It is a very tight fit and the seat belt on the Monterey can't be strapped and unstrapped with each use it must be strapped and then wiggled into and tightened. But they do fit.