My answer comes from the perspective of being an active member of Programmers.SE; a sometimes contributor of StackOverflow; and having some knowledge of Computer Science.SE as well as Theoretical Computer Science.SE1
For questions like:
I am of the opinion that specific questions concerning specific software should be permitted, queries such as: "My Creo Parametric model is giving a short-edge error. How should I go about tracking it down?" or "How do I create a variable-radius round in Autodesk Inventor?"
Of the SE sites I listed, both of those would be most on-topic at StackOverflow as they are implementation issues. Progs, CS, and TCS would all likely close as off-topic.
That said, I think a question on StackOverflow about parametric models would receive crickets in response. Seriously, just go search on "Creo" there.
There are currently 456 questions on SO tagged with Autocad, so the variable radius round question may pick up a decent answer from there. But 456 questions is pretty darn small for a tag on StackOverflow.
So it's pretty clear to me that those questions are in a gap that none of the existing software SE sites are addressing3. We've already established that we're not going to worry about overlap with other sites at this point, but I think it's worth pointing out when there could be an overlap but there isn't.
Blah, blah, blahTM - let's cut to the chase.
I think the parametric modeling question would be very much on-topic here. It seems like a question that's begging for an audience of Engineers to address. So, I would encourage questions like this one.
I'm a bit more lukewarm about the Autocad question, but I think that could be due to my "Programmers vs. StackOverflow" bias2 towards conceptual questions. I personally prefer to see more conceptually oriented questions and answers as I think they build higher quality content that's likely to have longer lasting value. This one seems more like a technician type question. OTOH, I could have also just revealed horrific ignorance there with using Autocad and other CAD systems.
TL;DR - Let's give 'em a run and see how they do. We can always narrow scope later.
1 What's surprising is the modest amount of overlap between the various sites... You would otherwise think there's lots of overlap there.
2 Note, I do like StackOverflow, but I much prefer Programmers. A simple glance at my profile will confirm that. I personally value understanding the why behind a particular approach more than I value an individual case of
how. That said, I do lots of research on SO to solve problems I run into during my work.
3@Gilles - please don't drop a network wide suspension on me for even remotely implying that CompSci is "just about software." :-)