Self centering

[alga]

You don't need to apologise, Johno, this is clearly on-topic. From your photo it does look like the wheel axis is a bit further to the front than the kingpin axis, and I assume Andy left the caster angle the same as in the Sierra-based wishbones.

Actually, it's easy to test-self centering in the stage you are in, just put it on the wheels, turn the wheel to the lock, and push the chassis a couple of feet and back. My steering wheel stays where it was on the stroke forward and unwinds a bit when pulled back.