Since kiddo can't ride
RF anymore, I personally would not consider any of the
convertible high wight harness options on
the list -- the Apex could be a good choice so long as the vehicle seatback provides head support at least up to eye level: consider the tallest setting for when kiddo eventually uses it as a
booster.... The
Regent would keep kiddo harnessed the longest, but I'm not sure off hand how easy it is to use in your vehicle since the new installation advice was released

Also, if you travel or if kiddo rides in other vehicles, then the
Regent will be too cumbersome.
What is your budget?