Some notes from my experience: N3DS Europe (AUS unit) (no hard mod but I'm capable of doing hard mods)
I went in fresh with the stock 4gb micro sd card. I wasn't about to play around with my filled up 128gb emunand monster lol! so I had to create title/import dbs for the issue in the next step since I had a formatted sysnand and created a new gw emunand.
While following the guide exactly when I reached section II downgrade step 8) I found that sysupdated failed to downgrade when using browserhax. So I booted up my GW and installed sysupdater cia. Then I booted back into ReiNand and using the cia it allowed me to downgrade. I'm sure it has to do with permissions and such
Downgrade was successful on first try.
as others noted step 15 of section 2 requires the exact file name - should be .xorpad. I also ran cmd as admin - just in case you don't know if you have to - doesn't hurt!
the hex editing is easy as pie. if you have any experience with a hex editor you can do it easily - my only experience with hex editing has been emulator save state hacking
restoring nand went smooth - made me a little anxious since this is the point of no return! upon rebooting the system it black screened. I tried again - nothing.... my heart sank...
I removed the micro sd card and tried w/o it and it booted up!
I followed section III and all worked according to plan - I didn't see any flashes but a rapid scrolling effect on the bottom screen. I waited a minute of that and then shut down. I opened my micro sd and there it was! a9f.bin 256byte file.
to restore:
I copied decrypt9's launcher.dat just in case - I didn't know if it was needed or not because I followed the browser restore files from
https://gbatemp.net/threads/otp-guide.415140/page-19#post-6084203
download the arm 9 and 11 bin files from there and put them on the sd card. I went to
http://dukesrg.github.io/2xrsa.html?arm11.bin and arm11.bin booted. the lower screen became a garbled mess of random colors for about 10 seconds or so. then decrypt9 menu loaded! I went ahead and restored sysnand through the menu options and my system is back to normal!
the process was relatively smooth - all the brick warnings, while justified, made me more nervous than the actual procedure!
thank you to all the people listed in the credits @
https://plailect.github.io/OTP/
Thanks for reading my story - hopefully it will calm you down and motivate you to get it done!