Here is my own spin on the low gravity AR code. The ones that I tried didn't work for me. I'm emulating a Gamecube with dolphin emulator, on a 64 bit Ubuntu machine. I came up with my own home-brew code that does the trick, but with a twist.
Here's an explanation:
123FBBF4 00000000 If any button is pressed (the main stick and the c stick both don't count, but the d pad does),
424057F4 05003200 Turn off gravity.
0A3FBBF4 00000000 If no buttons are being pressed,
424057F4 05003F70 Turn on gravity.
This way, if you jump and hold down a, you will continue upwards. When you release a, you will come down.
If you hold a button, say one of the buttons on the d pad, and walk off a roof, you will be suspended in mid air!
Sorry it's not encrypted. I was afraid that encrypting the code might cause issues.