Back in 89, when we did some Bucker Jungmans for the TOC, we also wondered about CG -best for aerobatics
The first flights, I watched as Rojecki flew some stuff and we commented on what looked good/bad.
The plane flew fine -tho a bit touchy- and when entering an upright spin it promptly fell through into an inverted slow flat spin.
It did this easily and predictably.
I said "waytail heavy"
Steve said "no"
on landings it floated a lot.
We changed cg to just aft the lower wing LE at the root. about a 2" forward shift ( 11.25" chord).
The plane was now very solid - did all the maneuvers and held spins - any type as input commanded.
I still fly that plane and have changed engines from a 40 cc to an 80 cc- -1-2 lb weight change but the plane still works nicely shifting from 16-18 lbs .
wing loading is in low -mid 20's ( 1790 sq in)
Bipes are strange creatures - The good cg range on this one is very broad.
BTW ,the model is exact scale except for 9% wing clip- a normal proceure on many full scale types.
(some full scale had fully sym airfoils -as did these.)