Thanks for the explanation which i mostly understand. But the idea of using it in a gupdate.gcd where the device doesn't have a 'conventional pre-boot mode' for RGN flashing is new surely? My friend with the GW has moved to Perth which is about as far away as you can get from me without falling into the Indian Ocean so i no longer have access to one of these Navis to play with. An unkind explanation for his move would be that he did it to stop me playing with his GW navi.
You probably remember that my interest in this topic is that i'm hoping the NT capabilities can be awakened in SP 2610/2650 like US fw v4.50/4.60 somehow does. Succeeding with that would immortalise you with a whole new group of bikers worldwide, and maybe i could bribe the local Hells Angels to stop terrorising me.