Most of your questions are answered in the Nav Rules. I have a PDF version,
which I can't find online just now, but the rules are online in HTML format
on the Coast Guard site. Go to www.uscg.org, and click on Favorites. (Having
a hard copy is a good idea, and I think often a legal requirement.)

You are right; on Truelove I am required to have a hard copy aboard.
I have several and have read them so many times I have about memorized
them, including the inland and western rivers rules. But thanks for
the link and the offer.

A short version, if I read them correctly, is that the red over green does
not replace but supplements the other, usual sailing lights, which then
cannot be a masthead tricolor.

You are right again. The red over green supplements the regular red
and green sidelights (or combination light at the bow). And, as you
say, one has to choose to use the tricolor light OR the red over
green, but not both at the same time.

It doesn't deal specifically with multi-masted boats that I can see.

That is true and another poster in rec.boats.building was of the
opinion that by saying at the peak of the mast it meant the highest
point on the boat. That poster thought that the wording eliminated
the option to put the lights on the mizzen. I am going to have to
research this some more.

Vertical separation is mandated at 1 metre for boats under 20 metres, and 2
metres if over.

In my original post I suggested that since the lights were optional I
might be able to get away with less separation. But a poster pointed
out and I now believe he is right, if one is going to have any lights
they need to be in compliance. Otherwise it would be better not to
have the lights.

How are lights not at the mast head made to shine "all around" - there must
be two lights, for and aft?

That is the technical problem. If it were just one light there would
be no problem. But when the red and green have to be separated by one
meter, it gets tricky to design so that the lights are not blocked by
the mast or some kind of extension. Another poster suggested just
what you have, two lights on either side (or fore and aft) of the
mast. I wonder if the lights would appear to merge into one from a
distance.

Thanks for your post, Charles.

Lee Huddleston
s/v Truelove