Thats funny, there's 3 or 4 posts related to Avistar and/or flaps going right now. I'll add my 2 cents here also. While I don't usually disagree with FH's comments, I will say that based on my observed experience with my Avistar the danger of stall spins is pretty low. i use about 30 or 40% throw max on my flaperons and you have to be moving very SLOW to stall the dang thing. I would say go for the flaperons and just start with small settings of 15 to 20% throw to get a feel for it, then move them up. Also, if you use slightly smaller servos (I used HS-81s) they will simply fit right into the slot for the original servo widthwise and you just have to shim them up a bit for length. This way you can always change back to single aileron servo later if you like.

On mine I have the stock 40 LA that I got on it when I bought it from the guy who tried to teach himself to fly (ok thats a whole other thread ). With the 40LA and a 10-6 prop a med-low idle floats it in quite nicely with no tendency to stall with 30% flaperons. I've done several dead sticks also and the flaperons do appear to make a noticeable difference in the glide angle.

Duke