I have a 40% FC Extra 330.

I had a severe wing rock problem in upright high alpha harriers.
You could not keep the wings from rocking.

I added4 ounces of weight to the tail and the wings stabilized.
Amazing! such a small little CG adjustment cured the wing rock.
I added more weight and the only difference I noticed was that waterfals became tighter.

Now that the wing rocking was cured, the plane still did not want to descend in a harrier because of the light wing loading.
Andy Kane programmed my radio for up reflexed ailerons when I hold down the "snap-roll" button and it cured that problem.
With the "spoilerons" up the plane would descend almost straight down.

So, I would say to move CG back and add spoilerons.

Barry Finck
Grantville, PA