The ArduCopter code only makes use of up to 8 channels at the moment. There are some vague plans to support more channels and there’s even an issue about it somewhere on the issues list.
There’s no way to use ch7/ch8 to adjust the circle diameter I’m afraid.
Feel free to add the request to the issues list but I can’t make any promises on when I personally will be able to get to it.
Certainly the pixhawk has a lot more growth potential, we’ve really gone over the limits on the APM. I’m not sure exactly when we won’t be able to stuff anymore features into the APM but we’re getting close.
I noticed that different Flight Modes are assigned to Ch5 (the three way switch for DEVO 10). I’ve seen a suggestion in a video on Mission Planer to assign Auto for the third position, Loiter for the second and Stablize for the first. My preference is to have RTL for the third position. Right now Ch8 does nothing to me. In the Standard Parameters tab I could assign AUTO to Ch8. Is this OK, meaning is AUTO taking precedence over any other setting for Ch5?
Thanks,