Extend scene lenght after camera motion tracking?

did a motion tracking and later had to extend the length of the scene:

plan a: by looping (pingpong) the final frames of the initial clip

  • can i obtain f-curves from camera solver constraint ?
    (or is it broken as mostly reported ?)

plan b: by repeating the last frame of the clip

  • can i extend length of the background source - movie clip ?
    (i seem to loose the tracking if i replace the movie sequence)