well i'd use 3 to 4 vertices, trying to form a perfect circle look, now depending on the speed is how big you want your helix to be, you can't go through a small helix going 60 mph, so after you create your ideal helix take something round similar to the size of the helix, and see if it is the same shape,look at the helix from all views, make sure your vertice handles look similar to each other, then go test, if it isn't to your satisfaction, keep adjusting the handles.[:)]