I would add "width of seat" because I run out of steering when the bars hit the seat.
With a skinnier seat/rider you can pull the bars further round their arc of travel.
If I take my seat off, the bars turn further.
The steering is designed using the Ackerman Steering spreadsheet and the links etc. are optimal in accordance with that.
There is <5% variance from perfect ackerman right down to 2M turning circles (which it cannot do anyway).