[jprince]

First six characters of serial number: G090G1
Firmware version before you started this procedure: 5.8.1

Feature related:
Was this Kindle registered with Amazon? yes
Was this an ad supported (Special Offers) Kindle? yes
Was a passcode set? no

Special sub-steps:
Did you clear the passcode before the downgrade? yes
Did you do the 'Reset (to factory results)' sub-step? yes

Internal data related:
Using the Kindle's Cloud Account or local or both? both
Where you using collections? no
Where you using bookmarks? no
Where you using annotations? no
Native language in use: US English

Kindle Hung:
What is the filename of factory initial update that was used? update_PW3_5.6.1.1_initial.bin
Which mirror did you get it from? mediafire
Confirmed the MD5: 07a7f86ad9ad72d3bea4f5de02685400

Approximately how long did the downgrade process run? 10ish minutes?
What was showing on the screen when it 'hung'? It cycled to boot, however, the "active" graphics don't fill the whole screen, rather the upper right. Perhaps as if it doesn't know its dimensions?

When the USB cable was connected, Kindle to PC, could you see the storage on the Kindle? yes, originally, however, after trying DO_FACTORY_RESTORE (and I mean, I did a touch -m /Volumes/Kindle/DO_FACTORY_RESTORE to create the file, it no longer seems to mount. However, the first time after that, it proceeded to ask what language I wanted to use. The graphics were/are still small, but the onscreen hit targets matched as if it were full size. Regardless, hitting Next lead back into boot cycling
What sort of response did your PC make when you plugged in the Kindle? originally, mounted via USB for a short time
Did using a USB-2 vs a USB-3 port on the PC make a difference? no
Was this same cable and same port working normally before the downgrade? yes

Normally, a Kindle is re-booted without any USB cable connected.
Leave the USB cable connected, Kindle-to-PC, re-boot Kindle (hold power button 40 seconds or more, ignore any pop-up panels seen).
What was the result? Same, now. Actually, 40 seconds doesn't seem to change anything. It continues to boot cycle as if you were not holding the power button, although, I'm not sure how that normally behaves. I'd not owned it long enough to have ever rebooted it that way


What OS and OS version in use on your PC: Mac OS X 10.11.5 (15F34)
USB-2 or USB-3 ports, or both? Both

Recovery:
If your PC could 'see' the Kindle storage (even briefly) try putting a file named:
DO_FACTORY_RESTORE
(all caps, no extension, no contents)
into the top level of visible USB storage.
Then use the power button to re-boot the Kindle
describe the result here: Described above


Does the 'hung' Kindle boot far enough to show the main screen, can you access the search bar? no

Other info: Actually, after reading other posts in this thread, my experience sounds very much like bloodien0se. The graphics I get pretty much match theirs—filling the upper right of the screen, as if it were using graphics intended for the Kindle PW version with less DPI.