I get it (sort of) that safety isn't your primary concern, but just want to caution you: It is my understanding that the shiny plastic covering on conventional Styrofoam helmets is there so if you hit the ground with forward velocity (Duh?), your head will slide after impact rather than the Styrofoam catching the asphalt and you breaking your neck (generally to be avoided if possible). Don't have any data to back this up but you might be statistically safer without a helmet then modifying one that may behave in ways you don't anticipate.