I am trying to decide between the Synapse 19 or 25. The smaller the better for me because I like to stow my bag under my airline seat. But, will the 19 hold 2 pants, 4 shirts, 3 socks, 3 underwear, sleepwear and 3-1-1 bag? Or do I need to go with the larger 25? And if the 25, will it fit under most seats (yes I know they vary)Please advise.