Sure. Right-click on your movie window. Then select:
"Subtitles --> Subtitles position"
Default is set to "Auto". Select "Select" and now a target subtitle will appear on your screen. Move your mouse up or down. Click when you get your loved position. ;)
It isn't possible to display subtitles UNDER the movie that way (in the 'black' part of the screen'). You'll have to extend the movie-dimensions some way, but I guess that isn't possible...