Here's an answer from Nicolas:
"the problem is that formatting requires using the "write track" FDC command, which is not supported for ST/MSA format so far where only sector content is stored.
But when I added the Pasti/STX support, I also added support for write track. In that case a .wd1772 file will be created that records the write track / write sector commands and act as an overlay of the STX file.
So, using the STX versions of Cadaver and Powermonger should work."