I've uses eclipses to design the shapes. and joined them up in variety of ways. I also have added the centre line to make the shape straight or sway in the direction I wanted it to be. 

I used a technical pen to outline the shape. I have used thicker line for the edge of the shape that we cant see the back and thin for line for places like corner. As you can see I have also fineline my centre line but I decided to make the line thinner.

I have added shadow as always. This time you can see that I have make the shadow lighter than before because I have got comment to go lighter on my shadow which I think now look better. I have also added highlight as always where I think it would catches light.