Maybe I've been in the hobby for too long but I don't see the problem or need for any special set up.
I put the sail control on the throttle channel. That way I can let the sails in and out and they stay put without having to keep a thumb on the stick.
For rudder I prefer to stick it on the aileron channel or the opposite stick from throttle depending on the mode you use. This gives me a dual thumb set up where rudder inputs do not impact sail settings and vice versa. Yes you have to keep a thumb on the rudder this way but for sailing you want minimum rudder when possible. And I find I adjust rudder more than sails anyway.
Other functions if you have them get farmed out to other switches and controls in what ever manner is comfortable to you.
The kicker in using a 2.4 system on a sail boat is to get at least one antenna as high in the hull/boat as possible. It's easy for waves / wake to block your signal when the boat heels. I much prefer using 75 MHz for my boats.
Scratch built on a surplus 6 Meter hull. 60 inch OAL. 22 pounds total weight when finished.
