Why not just copy an existing one from one of the player homes?
I simply made a new copy of the mannequin from the Actors list.
Copied all 4 objects from a player home.
1. XMarkerHeading linked to the Mannequin.
2. NobleTableRound01 from the static folder to stand on.
3. PlayerHouseMannequin which is an Actor and linked to the XMarkerHeading.
4. MannequinActivateTrig which is an activator. Not sure how its linked to the mannequin yet, but if you copy from a player house its setup correctly already.
You then click an object and press '1' twice to make it 'invisible' so you can select objects below it. Do this until you can select the PlayerHouseMannequin. Select it.
On the toolbar, use the >Edit >Search & Replace... feature to change that mannequin to the one you created.
It works for me.