I'm looking to replace my old shoulder tote bag with a rolling tote. I'm finding a lot of rolling totes that are sized 16x16x9 or thereabouts. These measurements exceed most domestic carryon sizes, yet they're marketed as fitting under most coach seats. I need to put it in the overhead bin anyway because I need the space under the seat for my feet. Seems silly to think I could legally take a regular carryon on board, when all I want is a smaller tote but those don't fit in the sizer box. What am I missing?