I have a an ongoing project with my F-12 EF-180B. [68' long 80m rotary dipole]. I scrapped the stock LL wires. I added a 17.5' long ....'T-bar' [capacity hat] 15' out on either side of the feed-point
Jim, these are the same issues that come up with mobile HF antennas and various loading methods. All of the techniques you mentioned will make the element electrically longer and that is what you are
In my opinion, that would be counterproductive. You don't get inductance out of a coil without current through it, and a coil will contribute the most shortening effect along a linear radiator wherev