Quoted from Djshakes:My suggestion is in your design you round the corners and maybe cut in on the other side of the hole entrance so it looks more like a backwards L. Might be more visually appealing as opposed to one solid square of plastic.
This was my original thoughts. But didn't want to spend time cutting and shaping if it didn't even deflect the airballs. Wanted to play it for a few weeks to make sure there weren't any unwanted side effects (like stuck balls, etc). Also made a smaller version for the back target to stop those airballs as well. After I find out how much to get these laser cut I would sell both as a package at pretty much cost of materials, labor and shipping.
And in all fairness, my design thoughts for this came from and original idea in a thread for POTC where someone wanted to remove the sneeze guard from the pirate ship. Much larger area with more curves and his design came out great.