I have a Kyosho GeeBee-Z and a 6-channel JR radio (JR-662). The plane calls for 4-channels, with 5 servos (a servo for each aileron). Could I simply plug one of the aileron servos in the 5th or 6th channel and have the two ailerons work as flaps when needed, at the flip of a switch? I'm assuming there's a function for this on my radio.

Also, if I do this, i.e. flip the switch and have both ailerons move down as flaps, would I be able to have ANY aileron function? Or does flipping the flap switch immobilize both ailerons in the down position?

And, lastly, the GeeBee-Z is a sport plane....a pylon racer I believe. I was thinking that having flap function would allow me to land it more slowly as well as fly it at slower speeds if I wanted. Is this correct thinking? Or are there other considerations that must be made?

From my own experience the flaps will work fine up to about 25 degrees and after that the adverse yaw gets to be too much to deal with unless you use rudder at the same time. Past 60 you can forget about any aileron action that works normally at all.

But most of the extra lift occurs during the first 25 degrees. After that it's pretty draggy with any further increase in lift.

Be sure to check it out way up high. You are basically increasing the camber of the section and along with that comes an increase in pitching moment as I understand it. The stab may not have the area to deal with the extra load.

Yep, you can do it. But also note that Flapperons can increase the chance of a tip stall. I'm not saying don't do it, by all means, go for it (I have them on several planes) just be aware of the tip stall thing (Watch that turn onto final).

Can you?
Yes.
Should you?
On a Gee-Bee.. NO!
Flaperons create tip stalls.
Adding a tipstalling device on a plane which already is fraught with tipstall capability..
How much do you like to repair?