Well he's just curious, and I've actually been wondering about this too.

I'd assume that it would work, but I wouldn't try it just in case.

When you use DevHook, it basically redirects any Flash0: call to MS:/Flash0:. I'm not sure if the downgrader would somehow override that, but I'd certainly choose to not attempt it.

Unless you're willing to brick your PSP, the world will just have to keep wondering. ;P