I've thought for years that the uncut panels were promotional or sales items.
If you're making a very large batch of cards a small sheet size isn't the best way to go.
What makes more sense, and fits the layout you've figured out is two "panels" of 40 5x8 cards on a single sheet with a wide margin in between them.
This 20 card panel shows portions of additional cards along one side.
http://feb17.hugginsandscott.com/cgi...l?itemid=13920
Doing it that way makes the printing reasonable, and the cutting easier. It even makes removing the 68 easier depending on how they did the cutting.