The X is supposed to automatically "sense" when the weight of someone in the passenger seat is inadequate to allow the safe deployment of the airbags. The side airbag even automatically renders itself inactive (and activates a sensor in the instrument cluster) when someone is leaning into its potential path. However, (here comes my unsolicited opinion) I would suggest never tempting fate on these things. The safe transport of the child is just too important! My son knows that he is not allowed in the front seat for years to come...for his own safety.
Sorry in advance.....I'm not trying to preach - I just feel strongly about the safe restraint of children in a vehicle. My son is 4 and 1/2 and is in a booster seat in the center of the second row and will remain in that seat until the recommended 80 lbs. No riding in the front seat until approx. 12 years old.
Considering my son didn't even reach five feet till the 8th grade (he's now five foot eight in 11th grade), he really didn't hit the 80 pound mark until probably 6th or 7th grade.
That would have meant he would still have been in his booster seat on his way to the school dance. How sad!
Just kidding, I understand your worries and for the average kid, the 80 pounds may be reasonable but for me, I don't think it would have been fair to put him in a booster seat on his first date and such. On the plus side, I did stick to the 12 year old air bag rule.
About the 80 pound thing - I just look at that as a general rule. I will let him use regular seatbelts when he is large enough to allow for proper positioning across his body. For my son, that will probably come quickly considering that Dad is 6'3" and my son is already 38". I should have said 80 lbs or tall enough - I stand corrected!
I do believe the center, middle seat is the safest. That is just based upon my experience of having been t-boned directly in the side (by someone who ran a yield green when turning) in an accident years ago. There was a lot of intrusion into my seating area (driver) and the car did not have side air bags (not that this is an issue in the rear seats). I just feel that when he is properly restrained in a booster seat in the center, the chances are less likely that he could be hurt by the doors coming in on a full side impact. Now, of course, it all depends on perspective......my son says he sits in the middle to have an excellent view and to fully enjoy the rear a/c (while fully knowing the rules)! Oh well, let him be cool.......and safe!
By the way, restraining anything with the pull down seat belt has not bothered me at all. I don't even notice it.