I'm guessing the duplicate you're thinking of is Water rocket physics.
Speaking as a non-moderator I don't think duplicate questions are necessarily a problem because often apparent duplicates are highlighting different aspects of the problem. In your case your new question is focussing on the nozzle design while the duplicate is more general.
I have sometimes answered questions I knew to be duplicates because I wanted to write about a particular aspect of the question and the older duplicate was different enough that my answer would have seemed a bit off topic there. For example Why does the refractive index depend on wavelength? is a duplicate of Why do prisms work (why is refraction frequency dependent)?, but I answered the former because I could pick up on some of the points mentioned by the OP and I felt my answer would be better there than on the duplicate. My answer got upvoted a few times so I guess others agree with me.
To return to your question, actually I think it's more engineering than physics and I'd be surprised if anyone can answer it without going off and doing the experiments. If anyone does know the answer I bet it's because they have already gone off and done the experiments. Still, I wouldn't rush to delete the question - wait and see what the site members think. If the question gets closed and attracts a lot of downvotes you might want to delete it because that cancels out the downvotes.