OK, I got a chance to work with things a bit more today. I now have some images available for download.http://www.tuxdriver.com/download/vdgtricks/
The bad news, of course, is two-fold: the diskette image is for the CoCo; and the binaries are for NTSC video.
I don't think any of my usual tools understand Dragon DOS format, so I didn't produce any such images. I could probably remedy that, if someone will direct me to some appropriate (and Linux-friendly) tools for that...
I don't have any PAL CoCo or Dragon machines. I think the binaries could be tweaked a bit to run on PAL, if someone wants to work with me on that. Some simple hacking on paltest1.asm should be sufficient to reveal what is necessary -- probably just increasing the count of non-displayed lines. Without such tweaks, I imagine you will only see a rolling mess.
In the meantime, if anyone has an NTSC CoCo or a Tano Dragon, then give these binaries a try!