Flying the blue flag or lite @ nite does mean owner is not aboard. It is how we invited our friends over (party time!) when the owner was absent in the days I ran the large motor
yachts, so it may be counter-productive to your needs. It was usually in tandem w/ a white lite (under a spreader) which meant "owner having dinner" which may work
better for your needs, but I know of no day mark for that one.
What a shame having such an attractive, interesting boat
Can you tell me who designed her, what wood
is she......? Sorry, I just couldn't resist.