Thanks. There is a bit of confusion around the hard disks used.
The CP/M 1 tools shown in the screenshot only mention the (larger, later) type H drives.
How did Corvus achieve 20 sectors on MFM drives, by the way?
B drives used IMI 6 meg native flat cable drives
H drives are IMI 5006, 5012 or 5018 which are ST-412 and a formatter board
it is clocked at 11MHz
see corvus_mfm_decoder.c in Dave Gesswein's MFM emulator source for details of the sector format