Questions about form design would probably not be on topic at Stack Overflow. From the FAQ:
We feel the best Stack Overflow questions have a bit of source code in them, but if your question generally covers …
- a specific programming problem
- a software algorithm
- software tools commonly used by programmers
- matters that are unique to the programming profession
… then you’re in the right place to ask your question!
Questions about UI design don't contain any source code, aren't about algorithms, and aren't specific to the programming profession. Thus, they would probably be better asked on the User Experience site.
While it's true that site does get less "action" than Stack Overflow, it's also likely that you'll get a better quality answer from the experts there than you will from programmers on SO. It may be a bad stereotype, but there's a reason that many of us are programmers rather than designers. My advice, though, is to make sure that your question is not overly technical and doesn't rely on any programming-specific details when you post it to UX.SE. As you mentioned in a comment, you can't assume that people know anything about programming or your particular platform. Copious amounts of example screenshots/wireframes are very helpful in setting up your question.
That said, questions about implementation, whether it's architecture implementation, design implementation, or database implementation, would all be on topic for Stack Overflow.
So, once you get past figuring out how the interface should look, and start writing actual source code, you can start asking questions on SO.