Call me a wussy all you want, but I value my PSP too much to try any untested hacks on. ;)
So, if anyone has a 1.51 or higher PSP that they'd like to try this on, go right ahead, but remember that it's untested.
Also, it's very doubtful that this will work, so don't be dissappointed.
This hack uses a KXploit-style method. It has one folder with a regular unsigned EBOOT.PBP and another folder with a signed update. What I'm hoping is that it will look in the % folder for the signature when it doesn't find it in the first folder.
If you have any other such potential hacks that you'd like to submit, please post them here.