You didn't say how much you droppped them. Play with small amounts, say 20°, coupled to the elevator to see how it acts. The idea of flapperons (and spoilerons) on a fun fly is to cause the plane to stall differently, so that more manuevers can be done, or done better. Few actually fly substantially slower with flapperons, and if you're just doing an offset with no elevator coupling (aka flaps), you'll get what you describe.