7
From the article you linked to
"The results have been very good to excellent but it seems to be very sensitive to the magnification ratio and amount of extension needed. "
That is for 67mm lens.
I'm asking because one can get surprises -- in either direction -- when playing around with specialised optics like these scanner lenses, CRT optics etc. For example, the Nikkor CRT 55mm f/1.2 is wonderfully sharp when used for its designated 1:4.4-1:5.5 range, but for infinity it is barely sharp just in the very centre, on the optical axis, everything else is pretty much blurred. For my Rodenstock TV-Heligon or Oude Delft Rayxar 50mm f/0.75 the behaviour is the exact opposite. In neither case the lens is a "generalist" behaving like ordinary lenses across a wide focus range.
All such behaviour makes of course playing with suchlike items more enjoyable and a little exciting. Stock up on the positive experiences and save the others for a rainy day.