Glass and Mirrors - How can I cut curved plexiglass?

I need to make a curved (top to bottom) cut in a piece of (side to side) curved 3/16" plexiglass. This is a motorcycle windshield, and I wish to cut about an inch off the top. The cut will curve to duplicate the original top line, and the windshield is formed into a curve. A good final appearance is greatly desired.

So...suggestions, please. I have a 1/4" die grinder, saber saw, hacksaw, cordless Dremel tool (with a dead battery), no band saw, and fair craftsman skills. I'll finish the cut edge with a file and sandpaper. I may wish to take another half-inch or inch off, subject to how I like the placement of the new top edge. How would either an abrasive cut-off disc or 1/8" diameter cutting bit work in the die grinder? I've had good results with the cut-off disc cutting fiberglass & gel coat--curves would need hand finishing.

(The recommended height for a motorcycle windshield is just below the line of sight. The windshield still deflects wind, bugs, rain, etc., over the top, but the rider's vision is over the top of the windshield that gets dirty, bug splattered, covered with rain drops just as one rides into bright sun, etc.)

Be certain that it is acrylic (plexiglas) and not polycarbonate (lexan). Assuming it's plexiglas, I would first practice on a scrap piece. The fact that the windshield is curved just makes it more difficult to make the cut accurate. I would use a jigsaw with a medium tooth blade. Do not use a fine blade since the plexi will melt together from the heat of the blade as you cut. You must keep the plexiglas from bouncing by clamping or the help of a friend. Protect the plexi from scratching by covering the area that the tool will pass over with painters masking tape.