I used the same technique using clear .015" styrene. I got a pack of 3 sheets of the clear styrene at my local hobby shop for less than $7. The cuts were made using an X-acto knife with a sharp new blade. I'm on my way to trying it with slightly thicker acrylic as well as PVC to see if I can do a better job with a different material. I'm also thinking about heating up the clear plastic overlay a little bit to see if I can stretch it to fit the HJC visor a bit better. Either way, the rough draft came out well:
If anyone needs it, I've attached the template I used to get the look that I got using Flying Squirrel's pep helm built to a height of 31.9cm. Essentially it's a modified version of the same template Sean posted in the tutorial, but I've spherized it a bit to increase the convex look of the visor. Hopefully this will be useful.
[attachment=2855:visortemplate1.JPG]