9:00 AM
OK, you made me think again about the exotic right leg circuit... I needed time to remember the idea behind this odd arrangement. I will reorganize my answer there and will create a post here about it. Now I'm moving to the blog to reply to your interesting comments there. Maybe I will redraw the conceptual circuit diagram...

1 hour later…
10:00 AM
Yes, I think both of us need to take a break and look back what we have been chatting so far. I agree that you might need to redraw you conceptual diagrams, with more descriptions on the test setup etc (Step 2 of my selfie walkthrough below). The Right Leg cct might take you a long time, because it was designed more than one hundred years ago, and some terms are inconsistent with today's usage.
I agree with you saying that my blog is getting very messy, and it is difficult to search things. So I have decided to make a summary in the new post:
I have been randomly hopping here and there, diverting aimlessly. Now I think your "Transformer + hand knob pot + scope" is in Lancaster's Elegantly Simple style and indeed elegant, but it is difficult to understand. So if you can explain it with your new enhanced conceptual diagram should help tunnel diodes newbies a lot. In the mean time I hope my use of the triangular wave would hopefully get the picture as by Tektronix (Step 7).
Ha, supper time. See you later.

2 hours later…
11:57 AM
TL Fong, It is a pleasure for me to read what you have written. I agree with it. You come out right - the right leg circuit takes time. I played with it because I lost something in my understanding. Here's how I try to imagine it geometrically - photos.app.goo.gl/dtK87WP9KduoP5nS6, photos.app.goo.gl/6X9ZPnTrTq6ej5AB9.

9 hours later…
9:06 PM
TL Fong, I edited my answer to the question about the right leg driven circuit. It would be interesting to make some "discussion" there. Also, I will copy it in my blog...