DS rides in his Beckett Nauti in our '10 Sienna. He gets indentions in his chin from the chest clip b/c his head falls forward while he snoozes. I tried "encouraging" his head to go to the side, but it always finds a way to bob forward. *sigh*
He's 3 yrs old and 37" tall.
We just took a road trip where we drove 10 hrs one way and 12 hrs coming back. Going, he had some issues getting settled in (this was his first long trip in the new seat and FF) and that's when the head started bobbing. It's probably just how he sleeps, though. I know I have seen him nod off and not have his head fall forward but he did it a lot on this last trip.
His biggest complaint is, just after I tighten his straps, he says, "I want to get OUT" and starts squirming. Sometimes, he says the crotch strap hurts (he'll say "Ouch! Dat hurts!" and I'll ask what and he'll point and say, "Down dere.").