If you are planning to build your cockpit windows I think there are two ways to get there. The upper edges of all windows are in the same plane. So you can define the needed hight and if you know the angles of the deviding bars you can build your windows from top to bottom. Or, like I did, you define the hopefully realistic angles of the window corners and the measurements of the window edges and build them piece by piece. Now I can adjust the whole window frame to my cockpit construction and support it with some temporarily pieces of wood instead of having the supporting wall construction finished.
My whole frame was made out of eight wooden bars 24 x 48 x 2000 mm. To cut accurate angles a miter saw or a miter sled would be handy.