I'm going to stay on 3.4 but wanted to update my CIOS and Homebrew.
I installed IOS58 from wiibrew so I could update homebrew channel to 1.0.8 or whatever the latest was. Then i ran CIOSX Rev21 I did 249 base 56 and am able to load USBLoaderGX (new one, old one wouldn't find the usb drive)...