On 15' Pro/Home domes, the weight of the shutters can cause the dome halves to tip inward at the top. This lessens the shutter opening width at the top of the dome.
When the shutters open / close, the Shutter Cable Connector Assemblies (SCCA) must push the dome halves apart near the top making it harder for the shutter motor to move the shutters.
This spreader bar design keeps the dome halves at a fixed distance and mitigates the additional stress on the shutter motor.
