I would think so. Personally, and this is aside from the rules or whatever, I would want as much side penetration protection as possible to prevent tree branches or posts from poking into the cabin area. Tubing will protect you from smashing into big immovable objects (impact accidents) but if there's no skin (like armor on a tank) then things that can penetrate will go right through. No tubing is going to protect you from a well placed pine tree branch, but another layer of sheet metal might make the difference. Just my thoughts on that, actual rally accident data ( if it exists) might say otherwise.