Assuming you have 3d modeling software, the answer is to rotate the pivot of your model relative to the Aurorabase.
Find a model that works like you intend and replace it with yours.
But before you do that, examine the pivot of each mesh and make yours like the one that works.
When you rotate (your) pivot be sure not to move it or scale it from where it resides in the model that already works.
What I mean is that it must line up exactly.
If your mesh is isolated (Not part of hierarchy nor attached to the Aurorabase) then after you rotate, reset the Xform.
Be sure to collapse the Xform modifier before saving.
Then check your nomenclature (chest000) in the model [delete the chosen working mesh] and upon the Aurorabase and link yours and the base together. [Alternately, select, insert and name a new base at 0.0.0 and check the correct boxes and then link]
Save & Export.
Before you continue, edit your 2da so all the particulars of your model are identified by the game engine.
As I recall, part models cannot have animation. So you may want to write a script to swap out the model at the correct time.
Or perhaps include it like an overlay (chest, belt, robe, vfx) so it might erupt through whatever the character is wearing.
Also don't forget to make some placeable corpses (Use some of the preset Bioware Npc models with your original non pivot rotated mesh)
Hope that helps !
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Ps Read and re-read the Custom Content Guide v3 by Elgio
