But, I don't know how to FORMAT a track with multiple sector sizes with
NEC 765 type controller.  Not as hard with WD style controllers.

On Mon, 12 Feb 2018, Eric Smith wrote:
Format a track with the sector size that occurs later on the track, with
dummy sectors ahead of them and gap sizes selected to position them
Start formatting with the sector size for the earlier sectors. Abort the
format at the time when the desired number of sectors have been written.
I'm not sure whether there's any way to abort a track format on a PC. I did
it on a machine that had control over the ??PD765 reset pin.

Thank you!

Definitely much easier with the WD style controllers.
It is possible to format disks on an NEC style controller with a format
that cannot be created on a WD style controller, for instance using
particular track or sector numbers above 0xf0, which are specially
interpreted by the WD during a track write.

I still feel that "multiple sector read/write" on NEC765 is less useful than "track read/write" of WD 179x.
In spite of WD's handling of what it interprets as address marks, etc.
'Course OUR needs are not always the same as the general public's, . . .

Is there any truth to the rumors that the choices of Data Address Marks (DAM-it!) on TRS80 was due to a misprinted or misread data sheet? And that Tandy wasn't a big enough player for WD to consider a variant of the 179X that could support those DAMs? We were not amused that the Model 3 could not write a true model 1 disk, and that Doubler, etc. had to contain BOTH 177x and 179x chips!

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