What CGRetired said..................

but keep in mind that glider guys have used a very slight flaperon deflection for years to fly their gliders a bit slower.

Using flaperons with what amounts to normal flap deflection can be a killer. Normal flaps for landing use a lot of deflection. That works because most flaps are less than full span. And actually give the wing some virtual washout. When you use the ailerons as flaps, you're not getting that washout, but the opposite.

(which is what CH said, only with the why in more words)