[Tired Old Man]

There has yet to be made a kit plane that is absolutely neutral. Every one will exhibit some type of unwanted roll, pitch, or yaw coupling in one attitude or power level from another. Just a simple change in propellers can impact flight attitudes and couplings.

One always has a choice in using or not using a mix. If they believe they are good enough to always anticipate and manually correct for coupling actions when they try to fly precision maneuvers without mixing and fly precisely. It's not possible but there are those that fool themselves into believing it can be done. They are usually the same ones with a computerized 10+ channel radio with all the whistles and bells, but with none of them other than servo reversing and end points utilized.

The effectiveness of a mix is completely dependant on how the owner sets up the plane. If they take the time to work engine thrust angles, using zero as a base starting point, nail the c/g, and have correct wing incidences, then any mixing will be minimal depending on the original plane design.

The choice to use mixes switched or always on is up to the owner. Many have found that some mixes, such as rudder/elevator for knife edge stuff, work just as effectively in other flight attitudes.