I can't believe this. It appears I may have solved this problem, just before I cut off my old Hobby Wing 40A pro ESCs and spent an entire weekend soldering on new ones.
The fast beeping of these ESC's indicated that on startup the throttle position was not low enough. The Taranis as far as I can tell has a range from -100 to +100. I tried to trim it past -100, and even set offsets and whatever else (had no idea what I was doing).
Then in another forum I found some discussion about the Taranis and the SuperX. Some users found that they had to invert their channels. This was not the case for me. I tried it, recal'd bla bla bla...
Right as I started to peel off the heat shrink on my first ESC wire to start removing from my 960, I decided to click on a "random" page. On page 187 of that thread a user said he had problems with a couple of motors which "randomly" decided not to arm, and beeped fast. This was what was happening to me. Once I was able to arm 5 motors, then 3, then 2, then 3, then 2... All without changing anything.
His solution was to set his throttle range at -90 to +100, then calibrate the ESC throttle range with that. Then he put the -90 back to -100 when hooked up to the SuperX.
BINGO. That worked for me. I've now successfully armed ALL F'ING SIX MOTORS several times.
THRILLED!