Ok so I took a crude measurement of the slop.
Here is what I did
1) Blue Sharpie rubber banded to the top center of the steering wheel.
2) Piece of wood behind steering wheel, just ahead of instrument cluster with a piece of paper on it.
3) Forced sharpie into paper and moved wheel back and forth until I felt resistance.
4) Did this a few times to make for good measure. As you can see on one pass I went a bit hard to the right and took the marker further beyond the initial resistance, this was an error.
This created a nice curve on the paper...that I hope represents the slop in the box. The sharpie was held nice and tight so that it did not tilt left/right as it was dragged across the paper.
Some things:
1) I know that the caliper measurement is not exact because the wheel is curved, but should be good enough.
2) I know that there is a decent amount of error that could be in this as well.
Here is the result. Let me know what you think about this approach and the result..
As far the interpreting the result:
Mercedes states that the maximum allowable slop is 25mm. This is to be measured with the wheel straight and the engine off. I measured 89mm linearly (3.531 inch = 89.70 mm.)
If I could flatten out that line it would be longer than 89mm.
So my conclusion is that the box has excessive slop and should be rejected.