LOAD ONLY SOLUTION
After using the nvidia-settings GUI just as user, edit the
~/.nvidia-settings-rc user file, and remove your host name prefix from all lines, leaving just ":" to start those lines. Just use replace all (your hostname) to nothing, in most editors.
Then, optionally set the file to read only; to lock any further changes. Otherwise
nvidia-settings GUI changes will add your host name back to the file, in multiples.
You just have to remember to set the file to read and write, to unlock your settings, so the GUI will change them again, if needed. Alas, then, you have to remove the hostnames from it again.
I use this to set a correct gamma/color (green cast) for photography editing, with Nvidia cards. My monitor settings don't do it right.
Why removing hostname works, I don't know; but it does! Now I don't have to close the auto loaded nvidia-setting dialog every time I boot up (without the "-l"), and the darn "-l" (that's an L for load only) option works; when
nvidia-setting -l is loaded as a startup application.