Well Jeff I clamped a stick of conduit horizontal and checked it for sag. It sags...
I also played with my 24 inch caliper and the ten foot stick of conduit and I think I'm going to go that route. The sag will be consistent and most the measurements I'm going to care about its more important both sides be the same than that I hit any particular measurement.
Black pipe might be stiffer, but it would be much heavier and I'd have to buy it while I already have about 40 foot of conduit just leaning against the wall in my shop...
