The usual constraints are performance and cost. In the case of this system's requirements the performance is measured by the ability of the frame to accurately align to the sun. Any bending of the frame would reduce the pointing accuracy, so stiffness needed to be optimized. Backlash from the drive mechanism is another issue, but that analysis was not covered in the scope of this analysis.
The resulting frame had an incredibly high stiffness to weight ratio, and was made out of commodity materials. Additionally, the base architecture can be extended into manufacturing into linear segments instead of rolled segments, thus affording for unpackaging and assembly on-site.
Constraints and wind loads of sustained 30 mph were used to evaluate the performance of the frame. The system needed to maintain angular pointing accuracy which can be resolved due to deflection of the frame under maximum wind loads.