Hi Phil,
nice model in a different livery
Concerning the nuts under the seat to fix the model in the display box: I do this since I use the boxes. That is a reason, why I usually don´t superdetail the chassis.
As voyager said: the model looks a little bit unstructured without panel-lines, and yes, it is too hard to use black on a white car. So I suggest to deepen the panellines with a hobby knife before painting the body, this gives more natural shadow and / or to blacken them before painting the body to enforce the shadow affect (like the preshading of the airplane modellers)