Tip for those who cannot edit the plist-files. Copy them using iFunbox to your PC. Edit them on the PC (using notepad or plist editor) and copy them back to the iPhone. I never worried about permissions or whatsoever and the modifications work fine. Only thing is to force the Garmin to close (doubleclick home buton and keep icon pushed until x appears to close). After restarting the App the modifications are effective.