We used stabilators on the F-15. It gave roll control at supersonic conditions when flexibility got to the ailerons and added roll control subsonically. There were schedules of control deflection with angle of attack and elevator input of course. With the stabilator, when the airplane is at large angle of attack, you can still retain control effectiveness. Think of an angle of attack of 25 degrees. Say it requires a pitch control input from the stabilator of 30 degrees leading edge down. That puts the stabilator at aabout a negative 5 degrees relative to the actual flow field (of course this is modified by the downwash term). The roll control available is maintained even at the large deflections.

For use in a fun fly it would work well if you get the mechanism worked out OK and if you can separate the two surfaces like the F-15 so that you have some good moment arms to work with. On a skinny fuselage there would be less rolling moment but it still would work. With one servo on each surface and transmitter mixing you could make it work fine.