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

How is it that someone like the OP can dangle so much nothing and get so much attention?

There is no relevance to what the OP has to offer other than the illusion of some secret sauce. It doesn't exist. The DF of an amp does not define anything, nor does the minimum impedance of a speaker. These factors are not predictive of anything.

And why haven't speaker and amp designers, who are ALL far more talented than the OP, come up with such "calculations" or "standard guidelines?" Because there would be no value.

Ok guys. This is going to end now and here. If your boss, of the cable industry you may represent wish to have a conversation, I'm here. For you: I'm no more available.