It worked for me. Old 3ds xl 10.3 to 9.2.
What I did step by step:
1) attempted downgrade, got error, tried 5 more times, no luck.
2) installed old version of ironfall to try and use ironhax.
3) ironhax gave me an error, so i couldn't install
4) I rebooted holding L ( to open homebrew on start up using menu manager)
5) attempted downgrade, no errors, all cias were installing.
6) 3-4 minutes later my 3ds rebooted, all my home icons were large (default) which was strange since I made them small. I also got a couple of notifications about setting up my 3ds. I knew something had happened.
7 I checked settings, and it was 9.2, it worked..., finally.