RULES CLARIFICATION UPDATE 10/19/2025:  Holes in the backstop for attachment purposes are allowed so long as the backstop remains fully solid. Using a CF tube to attach the backstop to the chassis may violate this rule due to the hole in the center of the tube. Please either fill the inside of the CF tube connecting the backstop to the chassis or use a 1/4″ wooden dowel or other solid rod to attach the backstop to the chassis instead.