The mid span pivot is actually the top of the press stack. As the fruit pulp compresses it begins to resist the beam making everything past the stack a cantilever beam. I'm not worried about the forces involved in the center span pivot as seen in the video because if the beam can handle the loads when used on the end pivot it will be fine when used on the mid pivot.

This picture really simplifies things:

http://2.bp.blogspot.com/-0AXOSJ1OcK8/ToX3fkUGaiI/AAAAAAAAAO4/KCYdx7XJu5Q/s1600/Lever+Press.jpg