On Monday, August 11, 2014 9:24:51 AM UTC-7, Leon wrote:

The problem here is very obvious Leon. YOU DON'T HAVE ENOUGH CLAMPS!!

I knowwwwwwww. LOL, The problem is that 8 footers are damn expensive
and I needed 4

The problem with C-shape clamps (including the adjustable-length ones) is
that the rib has to be stiff along its length. The wood handscrew clamps, though,
have one screw in tension and one in compression with no backbone required.
You can make a version of that geometry with a 2x4 in compression and threaded
rod (or a steel cable) in tension, that doesn't rely on the stiff backbone.

Even at 4', your (Bessy?) clamps are bowing a bit.