No one actually knows how to lculate what speaker cable they need

Mister b4icu...your snarky and condescending response is weird since I was simply responding to YOUR question, but based on your posts I suppose I really shouldn't be surprised. Bill Low on the other hand was helpful and respectful during our conversation, and the logical and well thought out descriptions of what these cables do and why they do it are succinct and relevant, and proven by their performance in my system. 

Regarding your lead-out termination and the issue of going from 0 awg to a smaller gauge wire - why bother with crimping, soldering, or a transition of any type to a different wire?  You could simply strip the insulation from the final 6 to 10 inches of the large wire, and then remove wire material from the perimeter of the bundle until you have the desired lead-out size that can then be covered with heat shrink for isolation and attached to a typical audio connector (banana or spade).  This would provide a direct connection from one end of the cable to the other without the need for transitions but still allowing the benefit of the larger 0 awg wire throughout most of the cable run.   BTW, Furez offers some copper connectors that have very large wire openings to keep the lead-out as large as possible.

Some of the large-sized (0 awg) wire I am looking at uses multiple bundles of wire such as in the linked example below.  If you count bundles, you can easily leave the same number of wire bundles for the lead-out resulting in a consistent lead-out size from cable to cable.  Looking at the linked wire picture, it appears one could simply remove the outer wire bundles and use the smaller inner bundles as the lead-out.

https://www.amazon.com/Gauge-Premium-Welding-Cable-Black/dp/B07CZ4VKG3/ref=sr_1_12?s=hi&rps=1&ie=UTF8&qid=1541181672&sr=1-12&keywords=1%2F0+Gauge+Premium+Extra+Flexible+Welding+Cable+600+VOLT+prime

I doubt many would claim that thicker wire is detrimental to the sound.

However we look at it, the narrowing of the conductor at the end is the weak spot. Theoretically, it has to be. Practically, maybe negligible. But many might say that for common cable lengths (2-3-4 meters) it is all negligible anyway. So, if we are talking in technical/calculations terms, decreasing the wire gauge must be of some importance. If we are talking about sound quality, it may not be important at all and the only way to find out is to listen to it.

Which makes calculations redundant and those who claimed that cables have to be listened to and not calculated, sort of, right.

How thin is that last connecting piece on the 0 AWG wire allowed to be before it can be considered a fuse? Should I ask that on some fuse thread? People there have some strong opinions about similar filaments' impact on the sound. 

I am not. I am barely a cable buyer. Every quarter of a century or so.

I really doubt there are many "cable professionals" here. b4icu did imply that geoffkait was also "working for someone" in that sense which even I think is far from correct. It may be a lot of windmills perceived here.