I'm not disagreeing with you, I'm saying that every old car is slightly different. Yes, I'm sure that little piece of fabric was added as a solution to the gap that was inevitable in some of those cars. I'm only talking about the area that 55bullit was talking about, and my advice to him and to anyone else is still that if there is no gap, no little piece of fabric is necessary. If there is a gap, utilize the piece of fabric.
I'm aware that there were pieces of tack strip sewed to the windlace assembly. BUT, those pieces could be removed from the assembly, clinched down under the tabs that hold them and the entire piece of windlace could be stapled or tacked to the now stationary tackstrips without anyone ever knowing. There is always more than one way to skin a cat, and with upholstery there are usually a dozen different ways. That doesn't make certain ways right or wrong, only different.
No one lives forever, the trick is creating something that will.