I'm wondering why using dd works for everyone else but not me. And wondering if something went wrong when I created /Root.

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Edited later to add:

Going through this once has reassured me that the patch to the firmware image with root access works fine.

Explaining how the mmc card is partitioned really solidified in my mind what I was doing.

Seeing that the complex steps are reduced to (A) a shell script that's easy to run and (B) a handful of commands to enter for a swapfile, I don't find this all that daunting, the way I did last week.

So, to eliminate the chance of problems from what I described here, tonight I'm going to start from scratch: reflash the 770, repartition the mmc card, run that script and make the swapfile. Having done it once, I can say with first-hand knowledge, "it's not that hard."