Gord May and Gord West...good sources of info! This is one of my favorite subjects partly due to the vast amounts of apparently conflicting information from the "experts".
Assuming that an automatic tuner functions properly, the two worst aspects of an SSB installation
is the radio frequency ground immediately from the tuner to the sea water
and the loss of energy from the tuner high-voltage RF output lead into surrounding metal such as pulpits and shrouds.
Yes, a flat copper conductor tends to minimize the inductance of the ground lead yet they are usually uncoated, easily corroded, and not easy to dress or twist to accommodate a run to a hull
fitting. They are also expensive. A better alternative is to use multiple parallel conductors for the ground "wire".
grade wire, 14 GA, like 14-2 or 14-3. Measure the length, in feet, from the tuner ground connector to the sea water
conductor through-hull. Divide the measurement by two and that is the minimum number of conductors to use for the high-frequency bands. For example, 8 feet divided by two equals 4 conductors. Use two 14-2 cables
or a 14-2 and an 14-3 to make the ground lead. Strip the ends of the measured wire and twist them together to make a single conductor at each end for the attachments.
Use nylon cable ties to "marry" the cables
intimately together along the run. This guarantees that the mutual inductance of the combined wires will cause the overall inductance to be the lowest value possible for the insulation
This technique is an improvement over that of the flat copper because it is relatively inexpensive, readily available, and easy to run in tight places and will not corrode. Imagine if the copper foil had many parallel "slits" in it's length that would not allow each adjacent copper conductor to touch its neighbor. THEN you would have an improved lower inductance lead than the strip with out the slits. That is what you have done with the multiple conductors.
Most SSB and HAM installations using automatic antenna tuners are designed to operate into a quarter-wave vertical antenna. The antenna "Begins" at the drive point which is physically where the ground and high-voltage wires exit the tuner. What we have just done is to create a "phantom ground" very close to the physical point of the tuner's ground lug.
When properly tuned, the high-voltage output lead is the point where maximum current flows. The current distribution falls off (shaped as a quarter cosine wave for you teckies) to zero at the top of the antenna radiator (which could be the bottom of your upper backstay insulator). Now here's the important part: The amount of energy that you can transfer to the atmosphere is directly proportional to the manner in which the CURRENT distribution "sees" open space without any surrounding metallic parasites. This means that if you run your high-voltage lead along the lower part of your backstay up to a lower insulator that you LOOSE energy into the lower backstay.
If you are smart you will NOT USE a lower insulator because of this phenomenon. Merely attach the high voltage lead to the inside chainplate contacting the backstay...you also save on having to drill through the deck
to feet a high-voltage lead. If you already have a lower insulator jump around it with rigging
wire the same alloy as your backstay using S/S wire clamps (not hose clamps). Do not put goop over the connections...leave them bare to the air. NOW you will not be pumping energy into a parasitic parallel conductor...you are USING the entire lower backstay as a radiator. There's not much that you can do to eliminate the loss from your stern pulpit.
What about the voltage on the exposed backstay? Here's the intersting physics that describes the voltage. The voltage distribution is ZERO at the turner output drive point and is desctribed by a quarter sine wave along the antenna, becomming maximum only AT THE UPPER INSULATOR!. The likelyhood of causing a shock is just about zero for another reason. You don't get shocked by RF you get burned only if you brush up against the upper end of the antenna.
I am very famaliar with RF burns having worked around 100kW SSB transmitters for several years. Anyway, why would you have anyone hanging onto the backstay when you are transmitting...their body, in proximity without touching the antenna, represents a "water loss" just like a parasitic parallel piece of rigging
...it reduces your effective radiated output power.
Now I realize that you will not want to trust to this explaination and will probably cover the lower 6-8 feet of the backstay with those plastic safety
line covers just "to be sure".
Pay attention to these few simple concepts and you will make a more reasonable installation
than you might otherwise.