I think you're on the right track. Differential ailerons help a little, but generally not enough. Keep working on your aileron to rudder mix. Manually coordinating rudder inputs with aileron can be pretty dicey and inconistent. I'm a lot more comfortable with a transmitter mix for those two channels.
You may have to experiment with your mix amount by in repeated flights, flying overhead in a straight line and then do a sudden bank as if to turn. Note which way the nose goes each time you begin the bank. If you do sudden banks to the right, does the nose go into the turn or out of the turn ? If the nose goes OUT of the turn, then you need to keep increasing the mix. Your goal will be to find the amount of mix where a sudden bank doesn't cause the nose to yaw left or right. Might take several flights, each time adjusting the mix a little more or less. When you get close to the correct mix it will become difficult to tell which way it's trying to go But by then you will probably be satisfied with the way the airplane flies.
Most airplane takes more mix for banking right than left. So your worst case will be for right banks.
Once you get the mix dialed in, the gyro may not even be necessary. But I think you will still like the way the gyro smooths out your flying.