I agree with AC7NJ - insulated backstay is the way to go on a sailboat. I have
done this on a number of boats here over the years.
If the boat is not to be scrutinized for off-shore racing, then one can do
it right -
break the lower end of backstay with an insulator right at the deck & place the
tuner under the deck at that point.
For some reason, common practice is to break the backstay a few meters up
from the deck & then bring a length of coax down from there. I would expect
that the aim of keeping the lower end "cold" will be lost as depending on
& frequency, the "feeder" could be awfully hot & will be coated in salt water
The likelihood of someone using the radio whilst crew are hanging on to the
backstay is slim & IMHO one can do better insulating with a shroud of some
sort - therefore being safer & electrically better.
Another sailing antenna solution I would like to try for somebody someday is
to put something like an IsoLoop on top of the mast.
W1ECT mentioned AA1XO/MM's boat is a bit of a dinky toy, so a permanent
antenna might be overkill, in which case I would be tempted to use something
based on my preferred backup antenna - fiberglass fishing pole strapped to
the aft railing: makes for a great wire vertical support & one can simply drop
a wire into the water to complete the other half.