I did what one poster said - but I put my backpack and my carry-on luggage in the overhead compartment. Then when my wife came (much later in the B's) I took my backpack out and replaced it with her luggage. I can't say for sure it was a dirty look from the Flight Attendant, but he did say "that was sneaky", and it wasn't in a joking way. So I am always a bit sensitive to doing that now!