Step 3 : create the ogive frame (in a new body)

Note: In reality the frame is built in three parts assembled together, but the objective of this tutorial being to show how to use external pilot parameters, it will be built here in a single block.
It's up to you to detail it if you feel the need.

In this new body, create a reference plane from the XZ plane.
Its position in Z (the normal to the starting plane in the local reference frame) is

        <<SketchBase>>.constraints.OpPlane

In a new sketch created in this plane and after making the "SketchOpening" 
master sketch visible, create a carbon copy of this master sketch
and then adapt it as needed.

Create an extrusion with a length equal to

        <<SketchBase>>.constraints.WallThickness

Create a copy by symmetry with respect to the YZ plane
of the resulting extrusion.