Therefore after much trial and error (read: about an hour of measuring and cutting while watching Scrubs reruns on WGN), I was able to create the EZ Visor Mod™.
I'll soon post a .PDF template so anyone can download and use for their own enjoyment.
Basically, at this point, I've cut out the mod using a garage sale sign I got for $1.00 at Home Depot (thanks to StormtrooperGuy for the sign idea). Then, using some of my wife's scrapbooking adhesive (Zots), I stuck them in place and viola!
Instant almost-screen accuracy in about an hour!
As you can see, I made them to simply cover the upper cheek area, from the frown up to the upper corners by the ear. It's a way easy way to reduce the overall size of the visor and make it slightly more screen accurate.
The particular sign I used has a slightly yellow tint, but regular hobby styrene is much closer to the Hasbro white. However, if you're going to give the whole thing a paint job, it doesn't really matter.
Also, I didn't bother to fill in any seams or bondo anything, as I didn't want to spend that much time or go to that much effort. I'm not trooping with this and I don't belong to the 501. I tend to only complete projects that I know I can realistically finish in less than a day.
In fact, I'm maybe I'll just form my own fan club - the Legion of Target Troopers. Haha.