Paul sound like you and your mentor has a good handle on things and he is guiding down the right road.

In hindsight and after going back to reread your first post there is another possibility that has not been mentioned in this thread yet but happens more often than you think even with well experienced pilots. That is simply reversed ailerons! This is what makes the second opinion on the airplane set up so important.

I really, really try on every test flight to check this at least three times. First two times an initial look and a double check before proceeding to start the engine or positioning the airplane for flight. While doing the intial airplane inspection with the tail of the airplane pointing toward my face as if I were the pilot of the airplane and sitting in it. then move each control surface with the transmitter in a full deflection of each surface and hold it. look at that surface and see if is defecting the wing or tail in the desired direction. Next do the opposite throw just the same and do this for all the flight controls.
After checking all the other important things, push rods linkages and so forth including a quick check of the CG and fingertips are just fine for a last check, Then I will take another look at the control directions before it leaves the bench.

The last very important test is an important habit every time even with an everyday flyer that you may have flown many times is when the airplane is sitting on the ground just before takeoff (every single t/o every time) do that third quick control direction test with the tail pointing at you just before take off.

I am not saying that is what happened to your FW but it is definitely a possibility and a scenario to keep in mind.


John