'30 Roadster Side curtain questions

[roll of the dices]

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Hoping someone can help me clarify a couple questions I have with regards to side curtains.

I have noticed some roadsters have a double lift the dot stud at the upper part of the upper stanchion; however, I am not sure of the need for it. I don't see 2 layers of fabric coming together at that point.
Should there only be single lift the dot stud as the other in the stanchions?
I also see some of the vendors stating there is a need for 2 of these double studs/car in reference to the side curtains.

Also does the right side eyelet in the horizontal band (sorry don't know the name for it) share the same cinch stud with the upper left side eyelet of the rear curtain?

Pictures might help explain my questions. Thank you,