After spending some time with Google, I decided my best bet was to try growisofs from the dvd+rw-tools package. Unfortunately, this quit with a "Not an MMC unit" error...which baffled me since my DVR-A04 is among the drives listed as MMC compliant on the dvd+rw-tools homepage.
Please keep in mind that most of information appearing on dvd+rw-tools page regarding particular model support is based on user feedback. DVR-A04 was reported by somebody as working [after DVR-A05 actually].
2) The dvd+rw-tools homepage should mention the "Not an MMC unit" error text somewhere and suggest a firmware upgrade as a possible resolution. I imagine most people have newer drives and won't run into this problem, but it really should be mentioned somewhere for the benefit of people like me who actually do run afoul of it.
Well, I personally didn't even believe that there ever were non-MMC compliant DVD units out there. "Not an MMC unit" was expected to appear with e.g. CD-R units. I can drop a note to "hardware compatibility notes" page... A.