I have hardly no coupling issues with mine. I changed my rates from what QQ recommends with both low and high rates. I only have a little coupling when doing full deflection as in knife edge loops or similar. I still have no mixing and all normal knife edge is rudder only. I did try the recommended low rates and had no problem holding knife edge. My cg is at the rear most recommended, maybe even further back with no signs of tailheavy condition yet. I would adjust your settings to your comfort since everyone likes different setups, and adjust the cg a little. In the morning when I put the plane together I will check my cg location and let you know.

Lee