Cross Stabilizer is a must have for the SP3B
"I did some experiments. Experiment 1 This experiment was to build my SP3B power rack using the 2 default pull-up bars. I then went on the side, and pushed against the power rack. The structure moved a little. The power rack feet did not move at all. Experiment 2 In this experiment, I built my SP3B power rack using one pull-up bars on the front side, and the Gorila Cross Stabilizer on the back side. I then went on the side, and pushed against the power rack. The structure did not move at all. The power rack feet did not move at all. Discussion In most exercises like squat, press, deadlift, the force is in the opposite direction of gravity. So we don't care that much about lateral stability of the power rack. Conclusion From these experiments, I conclude that the SP3B should come with 1 pull-up bar and 1 back cross stabilizer instead of 2 pull-up bars. The Rogue RML-390F has that design. The Iron Bull Strength PR1-F from has that design."