There are a lot of anomalies in the regs. Our local car club had a competitor who had a "standard" road car (Subaru). It took many FTD's against cars such as a Porsche GT3. Because it was "standard" it was not required to have a roll cage of any sort (and, in addition, had only lap and diagonal road car belts). If the owner had installed a roll cage it would have made the car much safer in the event of a crash. But then he would have had all the hassles/expense of homologating the cage. Surely roll protection of any sort (approved or not) is safer than no roll protection at all?