best way to get a bone sync is to get the merge/import model you want to use the xref or FFE swap into.
auto rename objects imported.
group straight away.
Dump a blank material channel onto the group.
You will immediately see any issues with synchronicity.
In this model the only areas of interest in the upper/forearms, hands, that need work.
where the bones of the coloured model or the original model for the REF, needs to be rotated and possibly scaled for the model to synchronize correctly.
Body/Bone Sync....
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