There are many finicky tricks to render a sketch view at an accurate scale, but a one-step solution is to place a slab of known size in the rendering below the facade and stretch the sketch rendering to match this size when you paste it into an ArchiCAD view.
Or use the analytical elevation as a guide when you paste in the sketch elevation, then disassociate the elevation and discard the drawing lines, leaving the sketch image to scale....
Dwight Atkinson