Well you left out all the caveats.
I do it all the time, no problem. Key thing is while the drives
are HD capable (TEAC FD55GFV) I happen to have them
jumpered as required to properly run DD mode. In this
mode they are plain DD, DS 96 TP! drives.
Does setting that jumper cause them to write double-tracks,
then (as ISTR that the HD drives wrote tracks that were
half-width, and someone used to sell a software package
that wrote an HD-width track, stepped the head, then
wrote an adjacent HD-width track to create pseudo-DD
tracks)?
Hey, precisely what jumper is that?
-doug q