Now it is there: How to use the Nadir Adapter
Workflow is the same for Nadir Adapter NN3, NN4, NN5.
You have to use a special set up of the tripod with the panohead, demonstrated in the pics at the end of the video.
Use minimum DPD Distance to move the tripod sideways. In case you do not get free space between corner of the tripod and tip of the third leg, move further.
In PtGuiPro you have to set the Viewpoint correction for Nadir2.