possible psp v2.71 exploit

Ok i took a psp 2.0 update and opened it up in pbp unpacker then i extracted the files and opened up the PARAM.SFO in pbp unpacker and edit the names to say v 2.80 then i remake the eboot with all the data and stuff but i use the new PARAM.SFO I try iit out on my psp and it starts up but right when it is about to load it says game cannot be started

can 1 of u guyz help me!

I really want to downgrade.......I have 2.71 FW now

not going to work goto the firmware hacks/ modifactions forum. have a thread on this