Red, you may be right. From the site you posted i found the safety code. Nothing in there about a spinner. OTOH, When i built my Top Flight GS P-47 three years ago, included in the build instructions was a copy of the IMAA rules for competition. In included the need for a spinner or other type of prop nut locking type of device. It is possible that they have dropped it or top flight is just dissemination old information.