Please go through all the text carefully, I don't want to hear the same old reccomendation I can't afford to accomplish (such as "get a hard disk adapter") or any other non-specific answer. thanks

So I have OPL working with a 64gb memory stick (extra-formatted to FAT32 with "guiformat.exe" tool, originally exFAT drive as recognized by windows). It goes pretty well, despite the horribly slow time of defrags and slow loading times.

I tried formatting it to NTFS, it just gets stuck at copying files in Windows, I don't know why.
I tried formatting it to its original exFAT, OPL gets stuck at the beginning (loading icon keeps rolling in the lower-right corner of the screen).
I noticed the drive gets organized by OPL in various folders (CD, DVD, CHT, etc...) but I tried putting ISO and BIN/CUE files into it ... but it didn't work. Maybe this is totally useless, since it always require USBUtility or should I just rename the BIN/ISO files somehow ?

I know PS2 USB drives are 1.0 so I should expect low speed, unless I get a hard disk adapter I shouldn't expect much, loading times may be not a problem, but I got a game that works perfectly on PCSX2, but USBUtility just can't convert it ("ISO to GAME" mode fails everytime, error 131).

I wonder how can I improve the situation, for example : what filesystems are supported by OPL for external drives (such as this memory stick) ? which format the iso must be, and how should they be renamed ? Should ul.cfg be edited as well ?