just to add
i assume the jfw uses the same 3.55 keys and they didnt create there own or anything stupid (although this is D/H were talking about lol)
as you need the fsm dongle to work to do the downgrade if the JFW isnt the 3.55 keys then you will get stuck in fsm
i doubt the JFW uses different keys. but just to be on the safe side i thought i best mention it
if the o/p tries this then keep your origional dump safe.