I fly mine pretty radical with the cg at 1.5", and it still requires a good amount of down elevator to maintain level inverted flight. But once you get it in that "groove" its a piece of cake, it stays there without requiring a lot of correction.
I even bring it down on the deck inverted, hi speed...just rock solid...

I believe its just a characteristic of this plane, after all, it is a low winger with built-in washout.

I don't know how much down I'm using, I usually don't think about it....I too busy flying to worry about things like that...