The points I see which require further clarification:
1. Why does the controller board need to be powered on last? Is it a matter of establishing proper communication with the serial chains? Did you learn something with the S5 which causes the three modules in series to have issues?
1A. I have a follow up regarding this to say, if it is truly important to power up the controller last, then why not require the controller to be powered from a separate power source? Will it void the warranty IF the controller board is powered by a separate power source? I can see this being dangerous if that power source failed since none of the fans will run and I assume all of the hash boards will melt down.
This is a particularly important question. Although it's easy to speculate why switching the controller on last is necessary, it would be good to have it spelt out why, also is this advisory or essential? My concern, as well as the one above, is suppose there is a brief power outage everything will the power back on simultaneously, or are we expected to have an automatic time delay built into the controller power?