I have seen a 24 Hour Race March newsletter, which has a section regarding driver's names in rear side windows.
This states "At the Oulton Park meeting, a lot of the cars did not display the name of the driver in the style required in the regulations."
As the regulations only state a preferred typeface (5.17.3), but mandate the minimum height of the first uppercase letter, the only requirement that must be met is the height of the first letter
More misinterpreting of the regulations.....