Thanks, I'll work on installing USB Loader GX now. I'm guessing that SD card support is out of the window so it's flash drives or hard drives, right?
Cyan, the developer behind USB Loader GX, has said several times that SD cards could be done, but meh. He doesn't consider it a priority. What I did was the next best thing, IMO: I'm using a 32GB SD card on the front reader for GameCube games, and a 64GB microSD with a USB adapter on one of the back ports for Wii games.
I don't have many digital Wii U games, so the 32GB model has been far more than enough for me so far. I have enough space between the two SD cards to fit my entire GC and Wii collection, I have my official GameCube adapter connected to one USB port on the back (the USB for rumble is connected to my PC, because I never use mi Wii U without my PC being on either way) and nothing is connected to the two front USB, so the lid can be closed. Perfectly tidy.