Hi Larry
Thank you for your thorough explanation.
My boat is made from aluminium, I forgot to add in my first post.
So just attaching the tuner to the backstay is not possible.

A 23"/7 mtr whip would be possible, but consider it as very vulnerable.
Waves, wind, boat being knocked-down (it is a sailboat afterall), etc.
Losing the antenna seems very realistic.

So basically an insulated backstay comes out as the best solution.
(I don't like the idea of cutting my stays though...)
h


In article ,
Larry wrote:

backstay some distance up the backstay from its base, which may or may
not be actually grounded. Most rigging isn't grounded anywhere as that
costs boat manufacturers money and reduces profits, mostly for Brunswick
Corporation in the USA. I'm 3rd mate deck and engineering on two French
boats, one a Jeanneau 40DS and it's backstay has no ground, neither does
the backstay on the main of the Amel Sharki 41 ketch. I'm not using
insulators on either one of them. The tuner for the Jeanneau is inside
the hull to port of the steering quadrant with a plastic-coated solid
copper wire against the insulating hull to a tiny hole next to the
embedded plate the backstay is bolted to. The wire on the outside
simply goes to a clamp made to connect a ground wire to a conduit and
coated to keep the salt off it with clear spray. From the middle of the
marina in Charleston, SC, I talked to hams across Europe, South America
and as far across the Pacific as Perth, Western Australia on it. The
top of the backstay is connected to the also-ungrounded mainmast and
shrouds. It's called shunt feeding and the whole rigging radiates
fairly well.