When ya'll are cutting your shields, remember 2 things...
Polycarbonate (lexan) shields won't crack and run, but may have a coating on the surface that you have to be careful with. Some will "peel" from the point of the cut. I'm sure lots of you have seen these shields when the coating starts coming off. Sand the cut edge carefully and well.
If you have a lucite shield like mine, remember that the only reason lucite is used at all is because of its unmatched clarity. It Will CRACK and WILL RUN extremely easy, so don't give it the slighest chance. Using a electric sander may be all the vibration it will take to run a tiny crack from the cut edge, so until you have the cut edge smoothed somewhat using a block and sandpaper, don't use a vibration sander or a rotary sander. Been there done that.
What kind of saw and blade worked for you?
On Lucite: the finest toothed blade to cut it. Do not "twist" the blade too much in a curve, it will crack!
On Lexan: You will have to use a blade with fewer and bigger teeth than for lucite as Lexan will heat up and "melt" if too much friction/not enough cutting is taking place.
I would suggest a coping saw for lucite, a jigsaw or coping saw for Lexan.
If using a jig or sabre saw, make sure to put tape over the area where the contact "foot" of the machine makes contact with your shield so it doesn't scratch it.
By the way...for those of you that have "gradient" colored shields and wake up one day (when someone cruelly points it out to you) that your black shield has now turned to blue...and you get NO satisfaction from Memphis Shades except hearing them tell you that everything fades in the sun and you shouldn't have left it out in the sun, you can always paint the lower portion from the inside the color it was originally, and it will show outside the original color, or pretty close, anyway.
