I bricked mine this morning. some background - goal was to re-enable ak2i once I heard usa dg to 4.2. I did this:
attempted to update system nand past 4.5 because you can't dg to 4.2 from 4.5 by booting gw mode while holding up. then loaded up a 8.1 rom and accepted the update agreement. black screen brick on restart. tried a second rom - black screen brick. tried a third 5.x rom - black screen brick. then rented dream team cart - updated to 5.x then downgraded to 4.2. still ak2i inop - used cearps flashcardtimewarp.cia and now ak2i works.
fyi - I hard modded my sysnand for write and the 3ds does not blue screen. after triple checking my work I decided to just plug it in after waiting 10 second on 3ds start up and my pc recognized it and I was able to write back my nand no problem - as if it was blue screened.
at that time I had no emunand, and of course I had a sysnand backup from a few years ago (4.5)