Good start. Here's my suggestions:
1) Less feathering on the drop shadow
2) The drop shadow needs to be shifted more to the right and slightly down.
For reference, see this image of the theatrical subs from Empire of Dreams (taken from myscamore's thread; ignore the subs in the letterboxing):
--edit--
Also, the theatrical subs for both Star Wars and Jedi have this weird thing where, when a sub ends at a cut, it actually ends 3 frames before the cut. I don't know if you want to replicate that or not. It doesn't really matter to me, in fact I think it looks a bit weird that way.