Hope your friend made sure the a/c was fit for that type of maneuvring. Had a chap at flight school who did the same with our secretary (at night and over the montains...) in one of our standard 152/172s only to experience the engine to quit. The fuel system needs some gravitiy to feed the eng properly. (don't know details, sorry) After some time while gliding for some unknown place in the dark the windmilling prop regenerated a suction flow of fuel to just restart the eng in the last minute... Not really necessary.