After all this effort, your help and days of work on my part looking into rendering workflows and codecs, more than I would've otherwise chosen to, it turns out the audio sync problem was on the timeline in my source project. Not that I was so careless that I didn't check this early on. I did, multiple times, but I didn't see it there. I suppose what became obvious on a large set top monitor was not so obvious on a smaller computer monitor. Not seeing it there, I assumed it had to do with the encoding.
For encoding, I wound up with a rather straightforward work flow. Render from Camtasia to avi at project specs using their default proprietary video codec and 48khz pcm audio. Then I rerendered in Sony Architect Studio to mpeg-2 and ac3.
There must be a lesson in this somewhere.
For what it's worth, I found that:
- Importing into and rendering from Sony Movie Studio before importing into Architect was unnecessary and didn't add to the quality of the final product.
- Sony Architect Studio rendered a somewhat better looking image than PreL.
- The 3rd party open source workflow (Logarith -> hd2sd / avisynth -> virtualdub) didn't seem to make for any improvement and I abandoned it per Steve's suggestion above.
I have now been able to produce a DVD with acceptable quality. Thanks for all your help!
BillyB