Now that it's been cleared up for me that I can bring a 22 lb carry on bag on the plane for my flight that can go in the overhead bin, I'm wondering how picky they are about the other personal bag you can bring to put under your seat? I have a backpack that I want to bring but it doesn't fit their specifications of 10" x 13" x 8" It's more like 20"x10"x 7". Is that going to be an issue?