Ask yourself why you want flapperons... "Why do I want flapperons?".

If your answer is "for fun", "to experiment with 3D stuff", "because I can", then go ahead and install flapperons.

If your answer is " so that i can slow down for landing, get better take-offs, or maybe more stable, slow flight", then you do not want flapperons. The Avistar has fantastic slow speed flight. It floats, and if you use flaps then you probably will struggle to get the plane on the ground.

For typical usage (as intended by the designers), the Avistar is *really* good. It has one aileron servo because that is all it needs (you are not going to be doing 3D with the avistar....)

Frankly, the plane is not going to be any better (for it's inteded purpose) with the additional servo on the aileron. It is overkill.

gus