Back in the good old days before fancy radios you needed to adjust the linkage geometry to get equal throws or unequal throws, whatever you needed. The old ships that only used one servo to drive both ailerons via torque rods could very easily be set up to give exact throws and differential without resorting to dual servo's, endpoint settings and differential mixes, so it can be done mechanically correct first.

It's personal preference but I'd much rather spend 4 hours in the workshop getting the mechanical setup right, rather than spend 4 hours at the flying field trying to mix out the strange little things that are happening. With a correct mechanical setup you can get the deflections to match throughout the WHOLE range of travel and not just at the endpoint, very important if you want to mix in flapperons or when using dual elevator servo setups. Endpoints only get the endpoints the same, not everywhere else in between.

However, the final test is the actual measured surface deflection, and as much as I like the shed, there are times when one pushrod can be slightly longer or shorter than the other and I can't figure out why, but I've got happy numbers in the TX and the measured deflections are correct and matching so I just live with it.