Have tried using just the stab. trim and rudder in the sim a few times and it's not easy. Flying around is OK but setting up an approach and making a landing off it on the runway is quite difficult. The airbus test pilots have done it in the real aircraft during test flying and I suspect, like most pure flying exercises, it would be easier in the aircraft than it is in the sim. Interestingly on the latest aircraft (A340 5/600) the manual back up has been deleted and was never required for certification of the orginal ones.