Bump steer revisited

[totta Crolla]

In my quest to eliminate bump steer l have found something interesting.
It seems there is built in bump steer and not a lot can be done about it.
The problem centres around the caster/tension arm. As the arm moves up and down with the suspension so it necessarily creates an arc, this arc works on the track control arm moving it back an forth and this movement tries to take the steering knuckle with it and this creates a self steering effect.
I'm using poly caster arm bushes and these are not compliant. Maybe standard bushes would help?
Any thoughts from anyone?