There has been discussion about how to straighten warped hard fiber helmet bodies and visors. I had a couple empty shells in the junk box and decided to try some heat. I used a 1250 watt heat gun, not a hair dryer, and heated the offending area for a couple of minutes, moving the gun all the while. I then forced the shell over another shell of similar size, so the fit was tight, and ran some water over the shell to speed cooling. Worked just fine! You can be creative with what you use for the form. I moved around the shell doing a 6 inch area at a time. You have to be careful and not get the gun too close or concentrate the gun on a specific spot or you will bubble any original shellac finish. You learn pretty quickly. I am not sure if this will work in all cases, but it was identical on both shells that I tried. As with any restoration process, proceed with caution.
Ron
Ron