There needs to be a floor of some sort. They can't just be open. Either a tunnel covering the area or a belly pan under the chassis. A belly pan with absorbent is actually required in ProMod with a torque converter. Driveshaft loops/tunnels and SFI cases as required. Also driver suit requirements may be different if there is an exposed transmission in the drivers compartment. Just because it's not required with proper cases, doesn't mean a person can't use a blanket on some of this stuff.