Aerodynamic bike helmet!

Step 9 Add two more pieces of foam on the sides.

Again, using the hotwire was useful to get these pieces to match the curved sides of the helmet. I didn't bother with any holes for these two pieces; instead, more sticky tape did the trick (however you choose to attach them, just make sure the force from the hotwire won't cause them to pop off while you're trying to shape them).