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

It goes back to cable manufaturars, mostly provide no relevant data! to sales and the users. None will answer this!
Whay do you think that you own now the optimal cable to your setup?
I think I've figured it out. 

Mr.  ebm

All you have to say on the subject, is that I had typo?
It's not much from your side to bring to this table.
Just for the record, some others already paid attention and made this remark B4.
Are you the guy who mock those who stutter or have a limp?
You must be very proud of yourself.
Mr. dill

I've heard that there are people, that all there purpose in life, is to be a bad example. You fit quite well into that category.
Your place must be in politics. Audio is kind of small for you. 

Mr.  eichlerera

For DF=50 and length of 6 feet (2 m), you need a #16 AWG.

1. No need for speakers impedance. They are not in this game (speaker cable).
2. DF=5 is relatively low. It was common (40~) at Japanese amps and receivers of the 70's. 

Well, since my Fidelium Cable is between 14 and 16 AWG, looks like it passes your criteria. Plus it's skin effect issues are minimized.