OK, so, I've already successfully downgraded my 3DS to 9.2 with a 10.6 firmware, but after doing this, I was going to downgrade a friends as well. I was going to use Ninjhax to install homemenuhax. I put in all the necessary homebrew and boot.3dsx. After scanning the QR code, it seems to load, but then crashes to the home menu. There firmware is 9.9.0-26U. Tried fresh homebrew starter kit install as well, and the boot.3dsx is the latest version, 2.6.