On Wed, 5 Mar 2014, Terry Stewart wrote:
   (Tez was kind
enough to send me an SU.DMK, but it was unfortunately for a 
 DS diskette and my Mod
4 is not so equipped.) 
 
  Steve,
 Are you sure you're not mistaken here?  I'm positive that DMK image I sent
 you is single sided.  Matthew Reed's TRSTools tells me the disk is DMK and
 the size is 180k, which would indicate a single sided double density 40
 track disk?  Also, my own machine has single sided drives and I'm sure this
 is the image I used to make a real disk. Thirdly, CopyCat is for single
 sided disks and this is what I used for the copying. 
Oh, it's certainly possible.  All I can tell you for sure is that Tim
Mann's dmk2cw tool insists on writing a double-sided diskette from it and
it's about 2x the size of the dmk image I ended up making.  I did not poke
at it with any other utilities.
  I remember more clearly how I made a real SU4 disk
now.  I used that image
 I sent you, which as you would have noticed is not a self-booting disk, but
 rather contains SU4 as a file. 
I will pick up that thread again, but...
Unfortunately, my Model 4 dropped dead rather uncerimoniously in the
middle of the afternoon today.  So I need to get sidetracked fixing it.
Symptoms are strange.  When you switch it on, the screen fills completely
with garbage - looks almost like every character in the ROM being dumped
end to end.  Drive 0 keep spinning, but does not get selected.  Keyboard
is ignored.  Not sure what this is about.
  I booted the Keil emulator with a  CopyCat disk image
I have.  It's version
 4.1 and says on the splash page it copies single sided diskettes (and I'm
 assuming only single-sided diskettes).  I then linked the SU4 DMK image to
 drive 0 and put a real disk in drive 1 (which was mapped to a physical
 drive).  Pressed enter and the disk was copied.
 I then could use this disk on the Model 4 by booting in a Model 4 DOS (e.g.
 TRSDOS 6.1), inserting the SU4 disk in drive 1 and calling up the file.
 My Model 4 is packed away so I just tried this procedure with Matthew
 Reed's TRS32 emulator.  Although it created another SU4 disk image rather
 than a physical disk, everything worked as above. 
We are maybe comparing Apples to Oranges. If I'm following you correctly,
you have an executable file on a conventional TRS-80 diskette and you're
not having to deal with the oddball formatting of the original SU4
diskette.  This is likely why you had no trouble making a physical copy.
The image I was playing with is a JV3 of the original SU diskette (mixed
sector sizes within a track!) and I seriously doubt that any PC can write
one.  To the Catweasel it's just a bunch of flux transitions, so no
problem there.
  I'm wondering if your issues might be related to
the Linux-based software.
 I'm not familiar with those TRS-80 emulators or tools at all. 
Well, this is all new to me.  Amigas, Cocos and Apple 2s I'm
very familiar with.  TRS-80s are uncharted territory at the moment.
Thanks again for the kind help and advice!
Steve
--