Hi
I had this concern once too. However all the research I have done says that this is not a concern. I've learned from various places that a child has outgrown a rear facing seat when they either reach the seats rear facing weight limit or have less than one inch between the top of their head and the top of the plastic car seat shell. Leg length is not an issue. It's torso length that matters.
Here is a quote from Kathleen Weber, Director, Child Passenger Protection Research Program, University of Michigan Medical School.
"As a side comment, some convertible child restraints indicate in their instructions that a child should face forward when his/her feet touch the vehicle seatback, or alternately when the legs must be bent. This prohibition is not justified by any accident experience or any laboratory evidence, and we are hoping that these instructions will soon be revised."
This is taken from the technical section of the carseat.org database, Rear Racing, why important.
Here is a technical article by the same author. Very in depth, it covers all aspects of child passenger safety.
http://www.umtri.umich.edu/library/pdf/weber.pdf
HTH
Laurie (
[email protected])