Just a quick mention of the opacity issue in optical roll scanning.
My scanner is not bothered by Scotch tape repairs.  The tape is
sufficiently opaque that it is read as paper.

This is also true of the new dry waxed paper rolls.  They read just
fine.  If a roll is known to have lots of translucent repairs, the
illumination level and comparator threshold can be adjusted to control
the sensitivity.

Spencer Chase

 [ Very good!  You and Richard Stibbons have certainly done a lot
 [ of work on your process.  -- Robbie