A small buglet, but viewing a file at half or quarter resolution in the Editor with the Action Cam Lens Distort Effect - even if its doing nothing- shrinks the size of the viewed image, rather than just de-rezing it. I.e. you get a large blank area around a smaller version of the image.
Make the file into a Composite Shot and it works OK in the Composite Editor, and viewing it at any resolution, AA, Full, Half, Quarter, looks perfectly normal.
It also fixes the view problem in the Editor as the Composite shot on the timeline is now stretched to fit the full screen.
Export the clip from the Editor or from a Composite and it is full frame - as that's not using any scaling.
The other Warp effects work OK, although the Perspective Warp does soften the image quite a lot, even when it's doing nothing.