i got a psp 2000 with 5.50 firmware can i downgrade it ? and run 5.03 cfw? ''If your PSP is on firmware 5.50 up to 6.20 and fully hackable, follow the "downgrading from 6.20" step, then the proper 5.03 softmod step.'' how to know if its fully hackable ? on the list there is only semi hack ?