What to do when you only have a partial answer

Question

Many times I find myself with relevant, sourced information when I look at a question, but won't have a complete answer. For example, in this recent question, the question asked for when large-scale slaughterhouses became common practice, and rabbinical positions for and against them. I know exactly one thing about that, which is the source I linked to in my answer explaining how certain practices of large-scale slaughter worked halachically (based on a comparison to Erev Yom Kipuur). This is not a complete answer by itself, but it's certainly relevant to the question.*
I'm not the only one with this issue: see, for example, here and here.

So my Meta question is -- in a situation like that, is it better to:

1. Post an answer with just the information I have.
2. Post an answer with the disclaimer that it is incomplete. (which is what I have been doing)
3. Post a comment with the information that I have.
4. Something else?

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   *_{Other answers where I have done this include but may not be limited to here here and here.}

Answer 1

In my opinion, whether the asker delineated parts to his question (1. Why is this done? 2. How long has it been done? ― Answer: So-and-so says it's done because of such-and-such.) or not (What's the custom? ― Answer: The Ashkenazic custom is such-and-such.) it's fine as an answer and needn't be a comment. And it should be worded so readers aren't confused: so they know it's a partial answer.