With a tubing bender you can probably bend it in place. Trimming slightly to remove interference would be a better solution than, for instance, adjusting the bars to suit the shield rather than the driver. File off any rough cuts and dull the edges, then wet sand with 2000 grit wet-or-dry sandpaper.
Acrylic has this tendency to light from the edges. Custom signs are made using this principle and I have considered edge-lighting my lower wind deflectors with amber LED's. If you flame polish the bottom edge it will get much worse. I would recommend that you remove the windscreen; mask both surfaces at the bottom with masking tape; and, paint just the lower edge with opaque paint of the color of your choice. To test this prior to painting it, you can cover the edge with black electrical tape and go for a test ride.
Hard to understand his position on this since he comes across as the scientist in the bunch, but I guess it is what it is. If you want to finish the job that he started, you could re-curve it yourself by heating it uniformly with a heat gun and either bending over a mandrel, or you could heat it in place and relieve the tension on the mounts. Once you know the radius that you need, it is amazing where you can find a "mandrel". Heat it, then quickly cover the inside surface with a towel and form it over whatever it takes (a chair back, the arm of an overstuffed couch, a trash can, whatever). The normal thermoforming temperature for acrylic is 275-350F, however, for the little bit of forming (or stress relief) that you are doing, the sheet should start to be movable at 250-275F.
