Hi Kevin, sorry I missed your last post here.

You wrote:
> While Lyes solution at first glance seems to be a good one
> it is not giving me the flat windscreen that I want to achieve
> but a curved windscreen that follows contours of canopy shape.
> In the side view shown it needs be straight line and not curved.

If I understand correctly, I would still recommend using the basic approach that was shown there of building a larger and more simple structured surface first and then cutting it.

But if you want to have a perfectly straight line as viewed from the side view, instead of cutting from a shape in the Top, draw a line on the side and use that as the cutting object.

Here are some visual steps.

First sweep the larger shape same as lyes showed - this is with the 2 bottom parts as the rails and the central part as a scaling rail. That produces this:



Now switch to the side view and draw the straight line that you want to have as your exact straight line profile, like this:



You can now select the sweep, and then use either Edit/Trim or Construct/Boolean/Difference to cut the sweep by the line. Here I used boolean difference which cut the sweep into 2 pieces:




Delete that interior part that has the curved region that you don't want to keep, that leaves you with this:



As viewed from the side that edge is completely flat:



Now to surface that interior piece - if I understand you correctly you do not want to have any curvature there, so instead of sweeping a curved profile along it, draw a line at the bottom of it between the ends there:



Then select the line and the edge and use Construct / Planar to build a planar surface there:



The result is attached here as Canopy_flat_side.zip


Is that the result that you were looking for? If not I may need some more details.

- Michael