20 years ago I bought a second hand 10m production Prout cat with little or no modification since production. There was just a masthead tri-clour and a steaming light 2/3 up the face of the mast but no deck
level lights. After being challenged by several other boats whilst steaming under tricolour and steaming light I exhaustively searched the literature for verification that this was an acceptable combination because that's how it left the factory so assumed it must be right.
Of course it wasn't right. I retro-fitted deck and stern lights to conform to deck level lights and steaming light when motoring, followed later by a masthead anchor light i.l.o a lantern in the rigging
. I then made up an auto-switching box of relays etc. that sense when the engine
is running.This switches tricolour to steaming/deck level when motoring automatically. No-one shouts at me anymore. Well not about my running lights anyway.