First of all, great project, and a nice start! IMHO I don't think its so much the top is lower on the drawing as much as it is the slope of the A-pillar and the side glass.
It has more of a slope to the side windows, so it appears lower. I took a screen shot of both and put them in a word doc together and its easier to see.
Another observation is that the hood is higher on the windshield on the drawing than the model.
I'd say get as close as you can without losing your mind. I think you're on your way to a nice build.