I try to do this, too, although it's easier to aim the light down and to the right side of the MUP, so I do that 90% of the time. If I try to shield the light I end up covering the whole thing and not being able to see anything in front of me.
As I've been curious about this issue myself, I recently found this post out of Australia:
http://the-riotact.com/led-bicycle-l...e-paths/108054 I think I'm going to try that plastic hood idea. I have the same light as the OP.