Hi,
i am using vWii Mode of Wii U and i have a lot of problems with usbloader gx (r1262) and cfg usbloader (cfg70r78.11).
usbloader gx:
detects usb sticks only with ios251 (don't know if this is normal)
usb2.0 stick seems to work. (tried fat32 settings from the definitive vwii hacking thread)...