Sorry if I missed it but what are you doing with it? Off grid or stand by usage during outages? If making rocket science out of an ST is fun for you than have fun doing it. Myself, I am into engines but generators bore me to tears. Just gimme some power OK
The things these guys do with the ST really does amaze me, I'm just not into it if you know what I mean?
If your like me and run (2) STs for stand by usage protection of the head doesn't need to be complicated. I am wired for 220 because I have a deep well pump and it simplifies transfer between grid and back up. Because we never know who might turn what on and what might be already running when they do it I protected each winding with a properly sized breaker prior to the main breaker which is also of correct total amps. Actually they are the same amperage as the 220 max amps is the same as each 110V leg. So, if I overload one side of the 110 I am twice protected, is it needed? who knows I am NOT a 'lectric kind of guy. I am not certain that a 6/1 has enough power to damage a 5 KW head even if all the load was on one winding but that's another study for another day. My STs do not like it one bit when the loads get out of balance too far and groan loudly in complaint. Not sure if the groaning hurts them but I don't like hearing it. An AMp probe was used to check things out when we were testing and we moved a few things around that are commonly used during an outage. Now if you do not need 220 V George has a set up that really should be the cats meow for back up where the head is wired for 110V only (which the head loves and you have no balance worries) AND you can still use it to back feed the home grid panel by feeding both sides of the buss 110, not two legs but same one. If something wired for 220 happens to be turned on nothing happens as the potential is the same on both legs. Far better for somebody smarter than me to explain it but If I had no 220 needs I would re do my set up like this.
Good luck, have fun and be safe,
Butch