Just a quick entry to cover a point asked by Antonio about using templates.
I'll use an example of some leg components from a hexapod that I am working on currently. Here is how I made them to be accurate to each other, and also accurate to the design. I'll add pictures to this post when I get home.
The component is a joint between two servos, and is a complex shape - A circular section at the end of each joint with a curved centre brace between the two.
I will post a picture of it at some point, but it's essentially the middle leg joint of a bot like this: