Building it.
Panel resting on supports
After trimming to match defrost wires
Measuring for length of side panel. I cut the panel 55" long.
Side panel taped into position. Will be trimmed approximately as in original drawing (below), the yellow outline.
Original drawing. Yellow = side panel, brown/tan = spoiler panel.
The photo with tape measure rule shows the approximate position of the spoiler plane. It will be close to horizontal, likely not sloped as steep as the drawing. Rear edge position determined by template. Front edge position determined by view out of the mirror. Panel is cut oversize on sides and at rear to allow for adjustment before finalizing.
Rear view of side panel before trimming.