From what I've seen on multiple gliders, nose weight is very close to the 3 dimensional CG, fixed tail weight is similar.
Water weight in the tail has a small part (maybe 35%?) below the total CG, thus changes the total CG a tiny bit although 2 dimensional CG is still valid.

Is it really worth it?, I don't know.

No, I'm not an engineer, but I have some reasonable background.