We're going to Hawaii next week, and I'm still trying to figure out what booster to get for DS. I had planned on buying a backless affix, but I'd love for him to be in a HBB, for sleeping in the car if nothing else. Obviously HBBs are not FAA approved, and will count against us as a carry on. Does anyone have a compass folding booster that could see if it fits in a regular school backpack? I'm thinking if DS can wear it on his back through the security checkpoint, I can strap it to my luggage afterwards. Otherwise, we'll need to check one of our bags, which is $25 x however many flights.