I am starting to make a replication of the JNL setup.
I have the trafo, timer chips, and YES, i made a fully insulated innertube cell.
I had contact with JNL about this insulation and he mailed me that indead the innertube is FULLY insulated. Inside and outside!
Nothing touches water. (no leaks!)
I ran a capacitance test and my LCR meter showd me 1nF with tapwater.
(Didnt had destilled in my lab/garage...but soon that problem will be solved as well)
I will publishe pics soon!
br
Steve