I was wondering if you could choose the format hard drive option to erase all data, like 3.60, and then use a friends ps3 thats still on 3.55 and copy the 3.55 onto the reformatted [should be blank] drive, thus making a new 3.55??
firmware information is saved in the flash memory of the console, so regardless of the thoroughness of formatting the drive, changing the drives, etc, if you have 3.56/3.60, you wouldnt be able to restore with a lower firmware. the ps3 itself would say that you need to update with firmware 3.60 or higher.
even if you try to 'update' with a lower firmware, it just wouldn't work and will give you a corrupt error (cant remember exactly what the code was).
if you put a 3.55 formatted drive into a 3.60, it wouldnt be able to read it until you fix the file system through recovery mode and it'll be on 3.60 once it's done recombobulating the energymotron... or whatever.