In an other matter you should get a feeling about the lines of the object itself, contradicting those line is not always a good idea, the purpose of engraving is to enhance the support, to complement it, it is best done by emphasizing the existing curves, it will give more an impression of movement to the final result, you do not impose a preconceive idea to the object you adapt your idea to the object so the object and the engraving will complement each other.