I may have been wrong when I mentioned the license plates were the easiest part of the model. The radio antenna is pretty easy too... it is mainly a rehash of prior techniques, but is in itself a good example of how you might use HyperNURBS to create an object that you might ordinarily approach with a different method.
Things like antennae may naturally be something you consider doing with a method such as Lathe NURBS, for example, but this should prove it is just as reasonable to use HyperNURBS.
Create a closed linear spline that defines a small square above where the base of the antenna will be attached to the car. As we will be copying the spline points into a polygon object later, remember they must not have any tangential information... I always use linear splines with no interpolation for this... This spline can be a square as we will only need the four points to create a single quad polygon from.
Line up the spline vertically so that it sits above the surface of the car where it was positioned in the overhead view.
Project the spline to the XZ plane thereby transferring the point positions onto the car body.
Copy and paste the points in the structure manager from the spline object into an empty polygon object.
Place the polygon object underneath a HyperNURBS parent and add a smoothing tag.
Select the polygon and make sure the normal is facing upward away from the car surface.
Use various combinations of the extrude tool, the move tool and the scale tool to fashion an antenna base from the original polygons you build it upward.
I imagine this is similar in concept to lathing or a pottery wheel...
Throughout the entire process, it is just the one leading polygon which remains selected.
Switch to point mode and set the Y value of the points to be equivalent to each other... thus leveling the top of the antenna base off to be perfectly horizontal.
Return to the polygon mode, and the polygon at the top should still be selected. Use the extrude inner tool to create the top surface of the antenna base.
The first extrude inner sharpens the base edges, the second offsets the polygon inwards to the starting circumference of the antenna shaft. I also extruded the polygon down into the base so that when it is extruded back out to form the antenna shaft, there is a visible joint/seam...
Okay, I can't hide from the signal lights any longer... I'm running out of easy things with which to bide my time by modeling...
Extrude the polygon now all the way up to create the actual shaft of the antenna.
Remember to make a little box with the polygon cage on top of the shaft so that a little bulb is created for the top of the antenna.
Well, this render barely shows you anything, since the antenna is so thin... but there you go.
At completion, it worked out to be a pretty good way of building an object that would ordinarily be done with other modeling methods...
And you know, if you divide the antenna shaft directly in half with a horizontal knifecut... and then you fit a bend modifier to the antenna object... you can actually control the flex of the antenna as the car rips down old small-town roads with the oldies blaring out of the AM radio...
Of course you're on your own if you choose to model a raccoon tail... :-)