Persol
Your drag hypothesis requires atmosphere where there is none. SL9 did elongate over time, and also widened its separation on that axis. Assumption that an object is going to break up into pieces the same size and mass is flawed.
The excel program is incapable of demonstrating the +/- factors of XYZ trajectory factors of multiple sized pieces.
It requires a four-dimensional plan, not a two as yours only shows. The fourth dimension is the time necessary to achieve separation before impact. You are thinking, and that is what it takes, lots of thought. Keep in mind the basic premise that in space once an object is in motion it will stay in motion until some factor like atmosphere, or a gravitational field is encountered. The tapering of ends are only on a few of the chains, not all. The largest chains, say 40 – 60 km wide craters show no sign of this tapering.
WCF
The comments about these chains by scientists are words on the pages and must be read besides just looking at the photos. My eyes are tired, and my brain mushed, by all the articles I have read. Many of those comments show changes of attitudes over the decades as these types of chains were found and photographed. I would really like to see some of the photos of crater chains that are listed but we have never seen pictures of!?
There is much more yet to be learned and debated, I agree. I do hope I am responding to the real questions being presented here, of course the ones that are of obviously not I ignore.