Hi Malcolm,
If your CG is at the 90mm point it is already forward.
Niall has moved his Acuracy cg back and found it helped.
With my bipes I found the strut fits critical. The contact points on those struts have a very short chord (assuming they are the same as the Midrex) so a little slop can have the tips twisting as much as a degree or two. To move a 1/4 to a 1/2 degree needs very little slop indeed. I shimmed mine to true and very tight - it takes effort to push the pins into place.
I had previously done this to the Ventura and before I did it was as you describe - especially in pushes and pulls.
You saw the Midrex fly at last years TC !! - only you can compare but it was quite windy for that event.
Then there is the issue of the two wings having different incidences to begin with !??
With a very forward cg there is a large moment between CG and AC. I'm not sure if I'd like a set up like that working on wings with different incidences ??!
If then there is any slop at the struts adding into this mix then it's likely to make for a lively/busy cocktail.
I don't know if any or all of this is relevant to your current set up, but if it is then when you add an inconsistent outside force like turbulence the outcome is likely to be along the lines you are describing.
Brian