Mockup of a DJI Phantom 2 prop guard.
This is an approximate representation of a DJI Phantom 2 prop guard. It can be imported into your FreeCAD drawings to check that it fits with your plan.
Outline shape of an SG90 9 gram servo.
This can be imported into your FreeCAD drawing (Part -> Import CAD).
For example, you could import this file into a drawing of a servo mount to check that the servo will fit correctly. Alternatively you could even cut this "part" to from a block to create a servo shaped recess.