Vertical Position of Bass Bourdons in historical Tablature
If the tablature signs are set on lines, the additional vertical correction, that is senseful, if tabs are set above lines, should be deleted. Else the bourdon tabs are too far away from the lines.
It even could be senseful to set it even higher, but I think the deletion of this correction would be a good thing for now.
I will add a small patch for this (also in 2.2).