So far, I have 7 downgraded units, 0 soft bricks, 0 hard bricks.
Summary of each unit downgraded to 9.2U with MenuHax as the entrypoint:
1. Unit: Aqua blue o3DS
Original FW: 9.9U
Problems encountered: Black screen after downgrading.
Fix: Removal of SD card.
2. Unit: Black o3DS
Original FW: 8.1U (with dummy browser) then upgraded to 10.3U.
Problems encountered: None
Fix: N/A
3. Unit: Black o3DS XL
Original FW: 9.7U
Problems encountered: Black screen after downgrading.
Fix: Removal of SD card.
4. Unit: Pikachu o3DS XL
Original FW: 10.3U
Problems encountered: None.
Fix: N/A
5. Unit: Blue o3DS XL
Original FW: 10.1U then upgraded to 10.3U due to update message on the browser.
Problems encountered: None.
Fix: N/A
6. Unit: Red o3DS XL
Original FW: 9.6U
Problems encountered: Black screen after downgrading.
Fix: Removal of SD card.
7. Unit: Blue o3DS XL
Original FW: 10.3U
Problems encountered: Crashed at "Rebooting in 10 seconds" message.
Fix: Forced shut down after 5 minutes of waiting? Then encountered black screens upon boot up which is fixed by removing the SD card.
No plans to downgrade my n3DS XL though.
Thanks for this guide again!