I’d like to share my workflow about the creatiàon of displacement maps in 3.1
When you’re ready to create displacement maps in Zbrush
1 : Create a cage at the 1rst subdiv level. (Tool - Geometry -cage)
2 : If the cage is OK for you, simply extracty the displacement map.
3 if not, you can tweak it in Zbrush or in another 3d app.
4 : When the tweaking is done, store a morph target and Reproject the cage. (Tool, Geometry, reproject higher subdiv.) The details will be aligned to the new tweaked cage.
5 Go to the 1rst subdiv level, and Switch your morph terget, to display the cage again
6 extract the displacement map.
(generally, iwhen you reproject you geometry using the Reproject higher subdiv tool, you should always reproject a Cage instead of the subdiv level 1 to avoid some sliding on the geometry.)