I was wondering what the height limit on the Marathon is. We have the RA and so in considering the Marathon, my question is while the weight limit is a great 65lbs., how much more taller are the shoulder harnesses on it than the RA? Since some kids outgrow by height faster than by weight, I just want to be sure.And also what would anybody suggest for an alternative combo/booter seat which is good for the taller, skinnier kid? Thanks!