Not sure I correctly understand the question.Cure firmware was made from old boot and new core 6.10 firmware,using the garmincure3 made the rgn file,updated by updater.exe.
Quote Originally Posted by lolypop000 View Post
Do you use in cure tool custom made FW or you create new FW?
Tried this too.Found:nuvi13xxand14xxseries_regionfileonly__510.gcd 25.5MB that is bigger than nuvi13xxand14xxseries_GCDFile__580.gcd 15.7MB.Updated (downgraded) via SD card,still removable device in my computer....

Quote Originally Posted by dasilvarsa View Post
Have you tried to downgrade normal firmware via SD Card ?
Version 5.1 Gupdate.gcd is my choice.
Nothing is without risk !