It seems to me like you are going about this the hard way. Why not use the toolbox to disable it? Page 2 of the menu, 'Modify System Settings' > 'System UI' tab. Second from the bottom is the "Device Dashboard Icon" switch. Flip it!
That messes the spacing up. The back button is too close to the edge now. That's why I want to use the command.
Everyone else seems to have no issues using the code/command, so I'm wondering what I'm doing wrong.