DD1 is 5y4m and is 47" and 44lbs. She is outgrowing the radian and I was thinking about getting her a frontier. Is the the next best seat for her to still be harnessed in? I need to still harness her because is doesn't sit still and listens on her own terms ( she is autistic) so I see her needing a seat for awhile. Right now I have a FF chase, FF radian, RF scenera in my 3rd row of my 06 dodge caravan and FF marathon 50 and a snugride 32 in the captains chairs. If I can't get the frontier to fit where the radian in, I am assuming I can't, I was planning on moving DD2 who is in the marathon to the radian and putting the frontier where the marathon was. Then using the marathon for DS when I no longer use the snugride. is there a different harnessed seat that is worth the money? DD1 shoulders are right at the straps so I feel like I need to make a decision soon on a new seat. Even though when I bought the radian I said this was our last car seat thinking DD1 could use a booster when she outgrew the radian. Thanks for any help.