Well, what I did, is I cut the visor out of the molded helmet, used that cut out and built it up to extend the edges about 1/2 inch with bondo and resin.
Then I filled it in to make it like a big wedge so it was sturdy. I sanded the front smooth and stand it on the vac table.
After heating the plastic, it SHOULD just get sucked down over the wedge and then I have a new visor to cut out.. but my vac isnt strong enough. So, when the suction dies out, I just push it over my wedge with my hands and fingers until it covers the whole wedge.
When it cools, I pop the wedge out and cut the flashing off of the new visor and install it.
Ill tell you what, Ill try it again on a new kind of plastic I found thats A LOT thinner.. maybe my vac table will work. If it does, Ill do a second one and record and post it so you can see what I mean.