Steve, I believe that it asymmetry is one way to get it like the pancake coils having one coil bigger than the other while being still bifilar. So one coil comes more from the middle of the pancake.
However i'm thinking about and the bifilar stan proposed could be a way to do it better, cause you can develop high voltage thru the wires having 0 inductance so no coupling, magnetic field not being consumed. Again as it is connected non inductively the electrons would like to go in one direction while there is a flow of electrons in the other direction, maybe thats why meyer said he was restricting amps there.
I was thinking about, if it is not bifilar canceling each other, there is very lower possibility for the thing to work, because you would have losses of the magnetic field of the resonance thus lowering directly the Q factor, coupling dynamically instead, would not load the Resonant tank. Thus generating probably a hell of electric Power.
A good thing to use in my opinion would be a coaxial cable or bounded speaker wire, maybe 100 meters is ok. I would go for 300 meters so to keep the frequency lower... would give around 50mh in air depending on the configuration... Maybe is over rated...