I'll try to make it short!! My almost 6 year old is in a Regent. She is tipping 50 pounds and is in the middle of the third row in a '94 Suburban, no tether. She just moved to the top slots. I thought about getting ds a new Radian and giving her the pink one back but she is right below the top slot and it's an XT so the wings will be in the way soon. She has to be in that position. Here's what I have. Front passenger-16yo. 2nd row-7yo in booster (behind driver), 2yo rf RadianXT, 15yo. 3rd row-12yo, 5yo in Regent, 10yo. My 7 yo was in a Regent but there is no tt and he is about 53-55 pounds. He does great in his booster but can't buckle it!! Anyway, what is narrower and wouldn't NEED a tt for her? I know almost anything is narrower than a Regent. The two other kids back there appreciate the extra room they have with a borrowed Radian back there we've been using the past couple of days!!