The sway bar is a standard set up; attaches to chassis rails above the spring forward of the axle and the ends clamp on to the spring just ahead of where the axle mounts on the spring. The rear suspension is straight out of the competition suspension manual.

I'm not convinced it's the shocks either; see the video below. I flub turn 1 and didn't catch back up till 13:35. The spitfire and I dice for several laps, the right rear shock on my car came in done and so the car bounces up and down like a puppy dry humping a squeaky toy. The oscillation is quite different from what you see in the first video.

https://m.youtube.com/watch?v=wtHvOwCJ1FY

If you remember when I put the H190 in the car I found that the axles had way to much end play and the car weaved way worse than this. After watching the video I want to check the end play again just to rule it out but I'm expecting it to be fine as I just checked a few months ago. It could be a case of it just needing a lateral locating device. My problem is that this is the only race car I've owned with leaf spring suspension. Even my Formula 500 (uses 31 mm Kart axle) uses a lateral locating device. I also can't find anyone else whose experience this issue at this level.