My method of accessing files in general (not just Sonar files) is to work from a desktop icon of the file.
I have found over years of working with files that working from a copy of a file (renamed with next version number) is a wonderful way of ensuring I don't lose a previous successful version and allows me to go back if there's an issue in the current file I'm working in.
Long story short, I open Sonar files by double clicking the icon of a file from the desktop folder.
When doing so in Hopkington the Start Screen does not display - which is ideal for me.
If for some reason I actually open from the Sonar New or Open menu I do see the Start Screen. I think that's great.