When a control surface actually stalls, it becomes ineffective. Because the pitching tendency of most conventional aircraft is nose-down, the stabilzer/elevator is used to produce a downforce on the tail. If the elevator stalled during a positive 'G' maneuver, then the model would pitch out. As was stated above, a loop's radius would increase, or the model might even quit looping and pitch the opposite way, outside.

Full-size aircraft have used a variety of devices on the horizontal stabilizer/elevator to help them. The Boeing 727 has vortex generators on the underside of the stabilizer to help keep flow attached when it's at high pitch in relation to its relative wind. This makes sure it won't stall during times when high control surface deflections are needed, such as during maximum performance low-speed flight and landing.