Okay, looks like I was previously wrong.

As far as I know, this is the only way to launch Garnet with no status bar.

/usr/bin/gvm/gvm -a lnch -z 1 -O none -f yes

Garnet will appear on the left side of the screen and I can't seem to find a way to center it either.

Also, there's no way of getting the status bar back so I personally don't recommend starting this in such a way.