Hey Robert,
Boot into 10586.0 BASE.
Go to the XX folder in there (just on Drive C: as you are used to) and unzip the UpgradePatch file over it.
Done.
This is really all and no Re-Activation is needed.
Btw, I made this new procedure exactly for the RAM OS Disk users. And, it would be true that when you back up the MyW10-10586.vhd file, you can go back to the old version by simply adding that file (with its other name) to the boot menu. Boot into it et voliá.
My recent Ram os disk partition expansion should remain in place?
Oh yes. That is not related at all.
It really is much simpler than you expect.
Best regards,
Peter