Bearfoil, "What is a Hoop?"
That's a good question. There's probably a nice technical term for the fool tabs, hoops, whatever. At each fastening point for the VS there are U shaped piece attached at the bottom of the U to the spar. The VS has a hoop, or tab, that fits in between the legs of the U. A honking big "pin" goes through all three pieces when the VS is installed to the plane. SOMEWHERE in that old thread there is a fine picture of the assembly process that might clear up this question. If its poster still has it reposting it here might be a good idea, moderators permitting.
I hope the description helps. That also explains why I built the index card experiment the way I did.