Mild steel will give and bend (absorb) when hit. CM will crack over time, the reason for the X-ray requirements. My first car was MS but was hard to sell, the two I have now are CM because that’s what the racers want. Remember the number one rule, triangulation. Your 50 pound head in a 5 pound helmet flopping around to close to a bar in a wreck is not good. I don’t think 2” is far enough away, remember Dale Earnhardt. these are just my opinions.