Best place for CG along roll axis

After constantly struggling with a heavy nose in several aircraft it
occurred to me that having a fat pilot in front and nothing else was
moving the CG forward. I put some weight in back and moved the CG
further back over the wings, and handling improved greatly. Is there
a way (other than consulting a manual each time) to determine exactly
where over the wing is the best place for the CG? MSFS is kind enough
to show me a diagram with the current CG marked, but I don't know how
far back I should try to place it.

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