I would definitely not turn him FFing. My older DD was big like he is, and we went through 3 car seats to keep her RFing longer than 2 years.
When my girls started fighting getting in their car seats, we let them climb in. They usually climb through the front seats to get to their seats. We have a Britax Marathon, and my younger DD can easily climb into it on her own. I've bumped my girls' heads many times and had to fight them to get buckled. But RFing is so much safer that it's worth it.
wife to John (8/5/00) mom to D (7), A (4.5), and N (2)