I'm soon to depart for a lengthy trip. Most flights will be long hauls 747, 777, etc... but I will also have some short hops on 737 and A320...nothing smaller than that I think. I don't want to bring any checked luggage but I also want to have room for my clothes. What is the largest possible carry-on (dimensions-wise) that will fit in all these overheads? Thanks! Also any reco's on models would be welcome.