I've seen dipole antennas strung up the backstay (not terribly vertical, I'll admit) and they didn't work so well there for most of the reasons aforementioned. Perhaps that's why people gave up.
Do you know if anyone has come up with a reasonable Yagi for marine SSB - or is the world still stuck on long-line backstay antennas??
"Honestly, I don't know why seamen persist in getting wrecked in some of the outlandish places they do, when they can do it in a nice place like Fiji." -- John Caldwell, "Desperate Voyage"