Hi!
Many times when I have checked out my fellow clubmembers aircraft having similar problems like yours they have had a twisted wing with wash-in in one wing!
Soo..... have you checked each wing with Robart incident meter..
It could also be checked with the eye-balling metod but you have to be sure of what you do to see it!
As for lopping an aircraft ...everyairplane is capable of doing loops with full power and with full elevator, with no right rudder and no stalling at the top of the loop ......it is just a question of adjusting the airplane /elevator throw. And don't be satiesfied with the CG is as per plan .......always .ry it a little further back ...but do this after flying the plane a couple of times with the recommended CG location. It might fly better with the CG further back and with less elevator throw?!


Regards!
Jan K