You should remove the widescreen filter from all your shots. Finish your editing. Then
Or, create a black Color Matte and put a Mask Shape filter on it. Set the filter to the following:
Horizontal 100
Vertical 72
Invert CHECKED
Now rename the Color Matte to "1.85 Widescreen Matte" and drag it into your Browser. Put that on a video track above your clips and it will matte your whole sequence to around the equivalent of a 1.85 Widescreen Matte letterbox. To temporarily remove it to save rendering time, just select it and press CONTROL-B. It's a lot easier than putting on 100 Widescreen Matte filters, and much more convenient than nesting.
Nick Meyers has suggested that if you create the same widescreen matte in Photoshop, rendering times are even shorter.
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