I have H9 J3 Cub PNP, can somebody give me recommendation for how much to mix rudder with ailron for co-ordinated turns?
Thanks

Don't mix any until you see it's needed. Some planes need mixing, some don't. Even some of the same type but different manufacturers do or don't need it.

Dr.1

agreed.... use your thumbs and fly for a while... learn to use the rudder,, then you can add some later once you see what this plane does...

Any degree of aileron to rudder mix that you choose will only be perfect at one airspeed. At lower speeds, (landing) it won't be enough and at the planes highest speed, it will be too much. When flying inverted, the mix will be opposite of what the plane needs. I suggest just learning to use the rudder.

If you are an inveterate right stick only except to turn the engine off for landing kind of flyer and insist that a Cub accomodates your flying style, you might start out with 50% aileron to rudder mix and fine tune it from there. Cubs actually turn pretty well with rudder only.

I've got 30% rudder mixed to my ailerons (Program Mix #1 on a 9C Futaba) and it's about right to get rid of most of the adverse yaw in a turn. I've got the older H-9 Cub, flies about the same as the PNP; you'll also want to program some differential in the ailerons (more UP travel than DOWN), that will also help keep the tail from dragging through turns.

That said, I agree with exeter and b.l.e. about just learning to use the left stick for more than just throttle. Just program the differential, and do without the mix. Playing with the rudder is half the fun of flying a Cub, and you'll be a better pilot on other planes as a benefit. Although I still have the mix in my radio, I generally use the rudder and elevator to turn my Cub floatplane, or use opposite aileron to keep the turn flat, or to sideslip in a crosswind.