Yup, pretty much all that needs to be said.  If you really want to use the lfp, you're gonna have to use official firmware, but as long as you have a copy of Lumines and go no higher than 3.50, you can always downgrade.  Honestly, though, a used psp goes for about $129 where I am, it's getting cheap enough that buying a sexcond one isn't too bad.