Both of my kids are in Britax Frontiers in 5 point harness in my car and DH's car. One (girl) is 8 years old, approx. 50-51 inches, and approx. 47 lbs. Other (boy) is 5 years old, approx. 43-44 inches, and 41 lbs. Because we live very far from family, most trips are by plane. Over the years, I have installed various Britax models successfully in rental cars, but just can't bear the thought of trying to bring and install the Frontier. I have used the SafeRider Travel Vests for trips where the only time in the car is between airport and the place we are staying, but I would like something more for trips where we will do more local driving. Although I am not a fan of boosters generally (thanks to the Kyle David Miller video), I am thinking that we might need to invest in 2 boosters for plane trips. I have the IIHS survey results for boosters from 2010, but wanted some "real life" suggestions. Thanks!