Just to throw some fuel on the fire, you should know that:


1. To the extent that the device couples RF energy into your backstay,
the backstay will be as "hot" with RF as if it were attached directly.
In other words, if the backstay itself is not "hot" then the device is
not going to be effective. RF can travel through insulators and air and
even a vacuum (thankfully).

2. It is possible (though not particularly common, and thus of sparsely
documented efficacy) to simply connect the tuner directly to the
backstay without any special devices. The backstay is almost always in
more or less direct electrical contact with the mast at one end and may
be grounded or attached to a chainplate on the fiberglass. It is more
difficult to analyze this arrangement since often the mast, stays,
shrouds, etc. are all a part of the antenna. Many would argue that
because of their proximity even to an insulated backstay, they are all
effectively (or not) a part of the antenna anyway. But however one
chooses to view this arrangement analytically, the fact remains that the
device under discussion electrically connects your tuner to your
uninsulated backstay, mast, forestay, shrouds, etc., etc., without
providing any safety increment (other than that obtained by reducing
energy supplied to the backstay) over a direct connection. SGC for one
explicitly discusses this as an option for use with their automatic tuners.

3. A simple, informative test can be made by simply connecting your
antenna tuner directly to the base of your backstay, providing the
backstay is not grounded there. If you're not happy with the results,
the device is not likely to help. If you're concerned about safety,
which a different issue, you had better stick with the insulators, while
hoping that the uninsulated portion of the backstay that is accessible
to human contact is not of a length likely to act as an antenna and be
hot itself!

My apologies if all of this has been covered elsewhere.

Good luck!

Chuck