becus25 has just released his new addition of his custom firmware with this changelog:
* Added the section "USB".
* Added on this section "Toggle USB (Memory Stick)"
* Added on this section "Toggle USB (Flash0)"
* Added on this section "Toggle USB (Flash1)"
* For VSH (XMB) ...
o When you format the Memory Stick the PSP create automatically the folders ISO and MP_ROOT.
Installation instructions and other important details should be available in the file readme - make sure to read that first before anything else.