Generally, a design patent protects the ornamental look of the object, not the functional aspects, and usually requires having 6 - 7 views.  On rear occasions a sectional view can be included to show all the features.  Since capturing the look of your product is key to a good design drawing set, having someone with an excellent understanding of line shading and proportions is imperative.  Straight Line Services does this.  We have over 28 years of design drawing experience and rarely have an objection from the patent office on sets SLS has completed.