Hey there,
Very quick answer, changing nappies duty !
Luke, if you put your glider in a 45 degrees dive, and release the stick, if he go more down, your CG is too backward.
If he goes up, CG is too forward...
Idealy, the glider should recover slowly from the dive...
Of course, for a sport glider, aerobatic ones should stay in the 45 degrees dive (neutral..) etc etc...
So, for me, and as the test shows, you need to put a bit of lead on the nose, and try again...
Changing the incidence, up to a certain point, will only change the flying attitude of the glider, that's all.
As I said, CG and incidence goes both together...
Find the correct CG, Incidence will not matter.
Like the guys who always put a piece of wood on the stab to change the incidence on a mouldy, when the issue certainly come from an incorrect CG.
You should see Marcel Guyang changing the incidence of his F3F models putting whatever incidence, and fly like nothing ever changed on his machine by just adjusting the CG... After this demonstration, well, you simply open your eyes on this Incidence/CofG relation...
Fred