Other options- change the resolution to 1920 x 1080 in the settings and possibly resize the window by dragging the frame. I am not st my computer to test this, but for PC, the key combo is alt-enter to go to full screen windowed mode. I don't know if Mac would use the same, or command-enter?
Another option, if your display supports HD resolution, would be to try forcing it in the command line options. So, after the-w put a space and then -r:1024x768
Would look like this:
-w -r:1024x768
You can change the resolution, just use the format "-r:XXXXxYYY"
That little screen in the middle is not ideal - sure hope we can get a good workaround