Over in a French forum theres apparently a version of the Downgrader in Beta that stops at 98% (and no it doesnt get any further) i strongly advise not to use it and also i strongly advise to not download any files marked as downgraders unless the legit PSP scene say they work.
PSPs cost too much money to lose them by bricking them because of the want to run homebrew. If your so desperate to run homebrew then swap your PSP with someone whos not bothered. Alternativly go and buy a PSP v1.5 from a shop that sells them ( i do know that SuccessHK are advertising v1.5 PSPs on their site) or finally why not keep your PSP as ultimate handheld that it is and go buy a GP2X which at launch is boasting a Gameboy Colour emulator and Video Player and with all of the GP32 Emulation Scenes best coders working on Homebrew and Emulators it wil be a real killer console for the amateur coder scene.
So one last time dont download any downgraders and dont go messing with the flash dir on your PSP Memcard.