Downgrading 3.52 to 1.50

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Has anyone successfully downgraded 3.52 to 1.50 using the Lumines hack (is there any other way?). Looking at the Wikipedia entry for Lumines it says Sony fixed the exploit in 3.51. I just purchased my PSP and like an idiot the first thing I did was run the network update. Now after doing some research it looks like I might have screwed myself. Am I also correct in understanding the only way to flash any of the hacked firmware (M33 more specifically) is to start with a PSP running 1.50? I really don't want to brick my unit as I don't know anyone else with one.

Also once the M33 firmware is running is it possible to reflash the Official 3.52 firmware if needed for warranty purposes?

Thanks everyone in advance for your help!