I just checked, the mizzen backstay is 7mm 1X19. Not sure on the length but about 15m. The expense is not an extra metre or two of wire but the fittings especially the two insulators.
I just came back home from a quick visit to Amelia and had a wonder around the marina. Very few sailing boats use whip antenna’s. It is a motor boat thing normally. I noticed a few quality yachts such as an Oyster 56 and a very smart Dutch aluminium proper voyaging boat, built for high latitude sailing. They both used the same insulated backstay system for their HF radios as I use on Amelia.
Amelia hull 019 Aml 54 La Palma
Can anyone please advise (or point me to a resource) about the length and wire gauge of the Amel 54 backstay. I’m still considering whether to use a starboard backstay or whip antenna!