If you s-off your device with a xtc clip, or if your device shows s-off in its hboot menu Do Not downgrade your hboot to 0.90.00000 as you will hard brick your device.
I believe this is caused by the hboot being moved by one byte and damaging the display process. Same as the black screen recovery issue and the same way as if people with the older model and hboot 0.90.0000 could flash rom_2.zip and gain s-off by the radio upgrade.
The result of this downgrade is a total black screen, all fastboot commands will fail with status malformed by one byte and the device will be rendered inoperable. This brick seems to be the same as the Qualcomm diagnostic mode bricks but the "blind boot" a ruu's rom.zip method fails.
I can post pic's if required for comparison but there is not much to see....
Stay safe and dont downgrade, no benefits from it anyway