This was achieved by:
Placing a Construction plane above the Body and Sketching an appropriate sized Rectangle:
The Rectangle was Selected and drawn downward completely through the Body in one movement:
Note that in the following I have used the Cube Body, in my previous Post a replication more similar to your body has been used. Adjust the position of the Rectangle to remove a quarter of the Circular Body.
To obtain the Profile you need Select the appropriate Faces use Tools > Project onto an appropriate Construction Plane.
If this is in the incorrect position you can move the Projected Sketch or review the position when Adding the Construction plane to accept the projection.