Change Default Video Size
Currently, the default pop-up videos play at 500px width and 344px height.
You can change this to any other dimension you wish by changing the numeric values on lines 20 and 21 in the wp-content/plugins/videoshowcase/js/jquery.pbvideosc.js file.
Following are lines 20 and 21:
Only change the numeric value in the above 2 lines. Leave everything else as is.
Related forum thread: http://ithemes.com/forum/index.php?/topic/19110-change-video-pop-up-size-to-hd/