My addition to this is what I've said numerous times before. Flaperons reduce the effectiveness of the ailerons. When deployed, the ailerons move down in unison, as said above. Then, what remains of aileron action is limited by, subtracted from, the aileron movement at a critical time, which is during slow movement during an approach and landing.

As GrayBeard, Ken, Minnflyer and others said, they are fine at altitude, but use them when you need aileron control, is just not a good idea.

CGr.