so long as you always make sure there is a clear inch between the top of bubs head the top of the headrest insert........

In short my recommendation is a Meridian or Platinum Tilt and Adjust pre height markers....
Melbel our seat doesn't have a headrest insert, so would it be an inch from the top of the seat? Sorry if that's a stupid question I'm just trying to keep him rear facing as long as possible and want to get it right! I think it's just about time to turn though