Sorry to keep spamming updates, I guess rally suspension is really important to me and as soon as I get a significant improvement I want to share it because it makes such a huge difference.
So I finally discovered the weight distribution app and was able to calculate exactly what the suspension stiffness should be. This is less than 1/2 as stiff as it was. The only way to achieve this was to boost the ride height adjustment up to 0.5m at the rear and 0.25m at the front. I don't know if there's some reason not to do this but for now it seems to be working.