I have a 4 star .60 i mounted the engine sideways on just for this trick. I have had successful inverted rudder ground scrapes probably close to a hundred times. But ive probably landed upside down 500 times. It is hard to get the angle just right because once the rudder is on the ground you cannot rotate. My 4 star would just land inverted as sweet as you please. In all the times i landed that way i only broke 3-4 props. Now that im into profile planes its easy to do with an inverted harrier rudder touch