Hey TK 9468 stealing my wifes account again.
On the motorcycle lenses they should for the most part be the shap of the helmet. Most are injection molded to the exact size and shap of the helmet they go on but if it is to curved you can always heat it alittle to relax the plastic. Since my wife and I ride we have replaced several lenses in are our day. Since the helmet is fiberglass based you might be able to apply a few small screws to hold the lens in. I was making my wife a replacment fiberglass scout helmet and had to put a screw at each end to help hold the curved lens down.
Just my 2 credits worth and seeing how we dont take republic credits its not worth much
