A friend got into using the center wire out of RG56 or 58 (tiny sucker). It cost him nothing and he tried all kinds or oversized tubes. Silk, and brown Texas cotton tube was my favorite. Silicone was nice and FREE at the time LOL. I never tried teflon with his "Stinger". That's what he called them. They were not terminated, Mids and highs only. I used them on small planars, they were like razors. It was the 90s. My Mac tube gear loved them.
The old WE copper with woven cotton/asbestos cover sound nice too.
Regards