I have a 4 year old ffing in a xtsl and a 13 month old in a chaperone. The 13 month old is getting a little scruched in the chaperone so I am looking to move her to the xtsl and looking at a frontier for the 4 year old. Should I get the frontier or the sict? I'm a little confused about tethering and what weight you can use the tether to. Can someone school me on that or give me a link. I know the sict says you don't have to use a tether. Is this a plus for older children in this seat? I'm a bit confused and am looking for the best long term option for my tall girl. Thanks!