Addendum:
http://fsae.com/eve/forums/a/tpc/f/125607348/m/85510167411/r/85510167411#85510167411
read the post by james waltman. pretty much describes the situation. They got real anal about this in FSAE so we all have to go through a bunch of stuff to get crash approved.
Your best bet really is to back half the car to keep the roof from caving in on your head if it isnt subie strong already. Other than that fill your car with as much honeycomb as possible. You would be suprised what a 2" think layer of high psi stuff inside you door would do. Most modern saloon race cars do this as a light means of provided better proetection in side impact structures since their windows dont go up and down. they can stuff about 6 inches which is sweet. This is also what makes irl,cart,f1 cars so safe. In side impacts the carbon skins of the monocoque provide almost no strength to the side impact. They just have a sick amount of high psi honeycomb between the skins to absorb impact. Skins just prevent physical penetration of objects. Then again their allowable peak g is around 100g’s where fsae keeps in down to 20.