Fine. No .ef on concrete. We also should implement the same 5 second delay for getting out of your airplane once you are down (can't you hear the whines the first time someone is vulched because of this??).
While we are at it, no "successful landing" if you come down on concrete with no landing gear. That should be a "ditch." It is an unfair, gamey way to shorten your landing time to come in wheels up, so it should be eliminated.
Make all planes start in the hanger, not on the runway. Make them taxi to the runway if they want to take off. Just to make sure they do not "game the game" by taking off across the grass, put low walls around the pads.
BTW, I agree completely with Jaxxo, Hub, Flatbar, and BaldEagl.