I have the same plane and know what you mean. remember the switch J is the high and low rates switch. high rate give 100% servo movement. if you need more movement remember you can move the control rods on the control horns to a lower hole(closer to the pivot point) on the rudder. this will give it more travel. low rate gives only 70% movement. unfortunately, that's just how it is with the stock spektrum radio for the plane. you can't change anything. you cant change the gyro settings either. you would need to buy a different gyro.
also keep in mind when in intermediate mode, below 100 feet, its still operates in beginner mode. I do not know how it knows the altitude. but this is what the manual says.