My DS is 4 1/2 years old, 42 lbs and 42" tall. We have 2 First Year True Fits for our vehicles, and although he is still well under 65 lbs, his head is nearing the top of the headrest. I would like to keep him in a harnessed seat in my car since that is the vehicle we use most often. Is a Britax Frontier the seat that will allow for the most head room or is there another seat that would be a good option to look into? I want to keep DS harnessed because he often falls asleep in the car. For DH's truck I'm thinking we would be better off with a high back booster since his truck is mostly only used for quick trips in town and DS rarely falls asleep. thoughts? TIA!