I don't know much about downgrading PSP Slims or any restrictions thereof, but I can tell you for sure that you can't make a Pandora Battery + Magic Memory Stick on your own. You will need a PSP that already has a custom firmware on it in order to make the battery + mem stick combo. EDIT: I've done a bit of reading, and it looks like you'll have to check if you have a TA88v3 mobo (You can check with this tool). If you do have a TA88v3 mobo, you will not be able to downgrade no matter what (Dark_AleX explains why here). For now, at least. There's always hope for the future.