Someone wrote this but I can't remember who ....
"Here is a list of things you need in an airplane intended for upside-down flight:
You need super-duper seatbelts to keep the pilot from flopping around.
You need to make sure the airframe is strong enough to withstand extra stress, including stress in new directions.
You need to make sure that the fuel, engine oil, and battery acid stay where they are supposed to be.
You will notice that changing the cross-sectional shape of the wing is not on this list. Any ordinary wing flies just fine inverted. Even a wing that is flat on one side and curved on the other flies just fine inverted. It may look a bit peculiar, but it works."
