Musta confused some... will try again.   The plane is a mid wing WITH a semi symmetrical airfoil.  I started with some differential but(a little less than 2:1) increased it trying to make the roll rate better, which it now does....  roll rate is much better, but the plane has ALWAYS exhibited poor yaw performance hence I have to crank in lots more rudder than most.  Even when I get a decent bank and turn the back end is low....

I believe this is due to the motor being extended for better balance departing from the original design.  The spacers added by the PO push the engine out about 2 inches in front of where it should be located according to the plans.   When asked why, he said it was because the original location made the plane tail heavy and this minimized the lead needed to balance it correctly.  I think the long nose moment is responsible for poor rudder response, but doesn't explain the low tail position in turns.

KKKKFL