That could work to disable safe mode, but I'm not sure about how other settings on the 51 may be affected.
Also the settings file "DS 50 settings.rar" you attached above has safe mode enabled so that file won't work.
Disable Restricted Mode in the device's settings first then download "settings.db" if you want to try it.
I think it is better to just mod the 51's settings.db file to all of your desired settings and keep as a spare.
I am going to try to convert my 51LMTHD to a 51LMT-s or something like that to totally solve the issue. I'll post the results if I can make it work. Might be awhile.