'USB-Advance-Splitted' games need to be in the root.
It could be programmed to load from other devices, but the root is 'standard' for this format.
You also can use normal ISOs on USB, but the OPL-Team isn't sure what the filesize-limit is.
The structure must be the same like on SMB/LAN.
PS2 V7/DMS3 V2 (FW:2.4b7); Seagate Baracuda 200GB
PS2 V7/CC1.0 (FW:34 hacked v2 BM:2.1.6); Maxtor DiamondMAX9 PLUS 160GB
PS2 SCPH-30004R; NoMod+NoLaser
3xSony MC 8MB
MAX/Datel 16MB with Boot-CD
Custom FMCB 1.8b+ Beta-Build, my AIO 0.5, Sony&xRhino-Linux