I still say we can just add a big single conducter at the core of need be. Is we can do parallel
IMHO, Negative.
Think about the stuff we learned from Dale Pond (Sympathetic Vibration). Each strand of wire is acting like a guitar string and they are all resonating at approximately the same frequency, because of their length, thickness and tension. If you change any one of those factors, you will have to perfectly hit on a harmonic or the effect will be gone.
So to me, adding more conductors is fine, but all the conductors must be as identical to each other as possible. The half-n-half aspect of the copper core probably has to do with how the Lenz Law effect gets phase shifted out of our way. I think 007 figured this out. I also think the number of conductors we use should be a count divisible by both 2 and 3, which is why I suggested 18.
VBM:
12 = 3
15 = 6
18 = 9
15 is out because we cannot split it evenly, but it may work with splitting 9 for the coil; 6 for the copper core. I have no idea what effect this kind of configuration would do. Maybe someone would like to try it and see.