I'm fine with all what you said. Let's forget bifilar as it creates misunderstanding; my point is that in Stan's design L1 and L2 are always wounded in opposite directions and magnetically coupled and there is a clear reason for doing that, it's not a mistake in the patent's picture. The bifilar is just a particular way of crancking the 2 inductances because as you have noticed the way the bifilar are connected is creating 2 opposite magnetic fields, same behaviour you get with two regular coils wounded in opposite directions.
Bifilar is when you wind two wires in the same bobin cavity, in the same direction, they are side by side and not arbitrarily wound. There is two ways to wire the two coils, aiding or opposing, the magnetic fields can add to one another or subtract. If you wire then opposing, what you get is a non inductive resistance. Wire them in aiding, you will get more inductance than both because of the mutual inductace between the two coils.
You can not have one coil of a bifilar coil variable. If Stan had a variable coil in the negative side of the circuit, these coils were not bifilar wound. Most likely seperate coils. This is not to say they are not on the same magnetic core. You could have one along side the other on a ferite rod, one having a wiper arm.
It is unclear how the bifilar coils react when there is a cell in between them. The timing of the bifilar coils magnetic fields could cause some type of modulation and even thou they are wired opposing, because the fields are not the same or not at the same time, this may cause some other effect we are looking for. Stan seems to always have coils in the positive and negative sides of the cell. They also seems to always be magneticlly connected.
What we need to concentrate on is the diode; it opens the circuit after the initial charge of the capacitor therefore the system can only work if it is properly magnetically coupled otherwise there is no way to transfer energy from the transformer/supply to the wfc (the diode prevents that).
My conclusion is that if you put a diode but your vic transformer is not properly magnetically coupled the system cannot work and it's not a matter of tuning the parameters. This is why I'm asking how the vic transformer is being wounded by the forum friends having troubles to find resonance.
On the other side if you remove the diode the system can work but not very efficiently as there is energy flowing back from the LC to the tranformer prime. The principle is the same that happens in the tesla coil when the sparking gap closes the circuit too long because of air ionizzation. Both Dave Lawton and Ravi's replica of the wfc were working but way less efficient then Stan's one and guess what... they didn't have the diode. Also the original wfc, the one from which clearly Stan got inspired from Puharich didn't have the diode while everything else was almost the same...a part the words used by the inventors to explain their works.
Back to my question: how do you explain the way the diode works in the vic circuit? I haven't found any good explanation so far.