If the c of g test(45 up,etc as already described) is ok, it sounds as though the only probs remaining are the slight roll coupling and the canopy-pull on downlines?
If the existing downtrim on el doesn't cause a pitch to the wheels in K/E, why worry about it?
My guess would be that a small %age of down el -at-idle-throttle mix would cure it,along with the usual rudder to ail mix for the roll coupling, and,given the lack of easily-achieved incidence adjustment, would be the first things to try.