I'll post this in hopes someone might have an answer...
Plane is a ModelTech Giles 202 (don't ask me why I keep fiddling with this thing!)

I've added 2 degrees washout on each wing, which seems to help with it's tip-stalling. The two wing halves are 0.5 degrees different (right side 5 degrees positive to left side - and no, I'm not the builder...), which might induce a left roll... but it doensn't appear to.

Here's the problem:
When trimmed for straight and level upright flight, then rolled inverted, the plane rolls left. Aileron trim is no help, since adding right roll trim only makes it roll right when upright. With me?

I've tried rudder trim while inverted, however all that does is affect yaw - no roll coupling with such small amounts of rudder trim.

I've checked the wing to stab angles, and the wing tips are skewed to the right (as measured from the wing tip TEs to the stab roots) by 3mm. I guess that might give some right roll upright, and left roll inverted? But would 3mm really be noticeable? And is my thinking right?
It also rolls slightly right on inside loops, and hard left on outside loops.

If you've any idea what I could do.... anybody?
Thanks!