Curious on the protocol when placing carry on under seat. Recently had words with fellow passenger when I clearly had my leg and foot in the middle space before he boarded. He insisted on putting his carry on backpack where my foot was. I asked him if he was OK with me putting my foot on the bag since I'm 6'5 and needed to keep my leg extended due to old football injury. I also explained that having leg room in 1st class is the reason I pay for it. He didn't care. Thoughts??