How can I influence the initial size of a shape?

[StreifLicht]

When I insert a rectangle (dragging it from the "drawing toolbox" onto the sheet, the rectangle has a size of 500 mm x 400 mm.
My drawing sheet has DIN A0 format. The drawing scale is 1:20.
How can I influence the initial size of the rectangle (a shape in general)? For instance the rectangle should have 50 x 40 mm. At the moment ALL shapes I insert are too big. I have to modify all insertes shapes.

BR StreifLicht

[Thomas Winkel]

You could adjust the shapes as required and store them in your own custom stencil.