Guys,
I too have wrapped quite a few donuts, as experimental chokes, I like 4" toroids, everywhere from 2 henry to 8. Anyway, you hit on something that I've been observing and working on and that is the choke wiring permutations. You can shift much of the resonant waveform to the positive or the negative with the sizing of the neg and positive chokes.
for example, take any 110 to 12v or 24 volt transformer and connect it as a choke in the 8XA circuit, primary- one choke, secondary- 2nd choke. you'll see that by switching the choke inputs and outputs, aiding or bucking waveforms at resonance and and lopesided wierd looking rose flower bulbs grow on the screen. I find most gas production in this case happens when the smallest wave peak and trough that you can dial to is made into a more perfect smooth tooth by tiny adjustments. It looks like a jagged capital "A" and turns into a more smooth A and the most gas is produced.
$.02
kickbackemf