Nice setup.
The coil I'm using is from an old (30 years) power cable that has two wires which are not twisted. A spool of speaker cable would be a similar thing. It has mass which is important, because Tesla said that his experiments had better results when there was more mass (in terms of wire size). I still think that coils like yours and mine can provide much more than we are currently seeing.
As for the skin effect: Tesla said that this happens mostly at high frequencies which we are not employing in those setups. What is interesting to me is that I can't produce back-EMF from such coils at higher frequencies. I've managed to get some at a few kilocycles, but not faster. There are spikes at higher frequencies, but they are much smaller and I don't know if they produce any gain.
The coil I'm using is from an old (30 years) power cable that has two wires which are not twisted. A spool of speaker cable would be a similar thing. It has mass which is important, because Tesla said that his experiments had better results when there was more mass (in terms of wire size). I still think that coils like yours and mine can provide much more than we are currently seeing.
As for the skin effect: Tesla said that this happens mostly at high frequencies which we are not employing in those setups. What is interesting to me is that I can't produce back-EMF from such coils at higher frequencies. I've managed to get some at a few kilocycles, but not faster. There are spikes at higher frequencies, but they are much smaller and I don't know if they produce any gain.