RE: Aileron differential
I love this question - because the answer depends on what you are trying to fix.
on a heavily loaded slow model the answer will be extremely different -ascompared to a very lightly loaded aerobatic setup
If yo are a contest buff who is looking for the best appearing roll - yet another answer
Some wil swear that the model must have all forces in line to get a perfect axial roll - not so - I can show you rolls with a 526 AFS Zlin which has a widely seperated force setup and the rolls appear perfectly axial-
why?
because the rolls all have the spinner and aft fuselage in an apparantly straight line.
An optikal delusion---
unloaded rolls (vertical appear different than rolls with the wings loaded so that presents another setup-for best appearances.
basically the model which needs least AOA for a roll will always look the best -