Hi kevin,
No numbers, just some observations. After his first flight in a Duo Discus, a

One of our motorglider pilots pulled many pounds out
of the glider nose and liked the results.

When I flew my 172 for 400+ hours in 2 years, I noticed
that certain C.G.s were better. All the way aft legal
was too much, I think because the forward trim was so
much that the angle of elevator to trim created a lot
of drag. But 3/4 aft worked VERY well. It was
amazing how much faster it cruised and how much easier
it was to to trim and to flare with 3/4 aft CG.

I flew a Twin Commander with a forward CG problem.
I didn't notice until I got to fly a different Commander,
and the controls were light. It seems this one still
had the old radios left in as ballast in the aft.
It was a totally different feel.

Beware of old weight and balance sheets. The actual W&B
may be quite different but the owner may be reluctant
to reweigh it, since many aircraft lose quite a lot of
useful load when officially reweighed.