My 10 month old so far off the charts in height, he was the size of an average 17 month old at his 9 month check up. We have the Clek Foonf and even rear facing, his feet are only just touching the back of the seat, not scrunched at all. I really like it a lot. We had a Britax Marathon that I ended up getting rid of because it was a terrible fit for him. I got it for my baby shower before I knew I'd have a giant and that Britax shells are generally shorter so not recommended for tall kids.
One thing with the Clek Foonf, though: it's really tall so if you have a smaller car, you will likely not be able to make it fit rear facing without having the seat in front of it rendered useless. Definitely check the dimensions first.