My SawStop ICS has two 2.25" branches that come off of the 4" main dust port. One is for the overarm setup on the saw and the other is for the fence on a SawStop inline router table dust collection box. The branch at the router has a lot more air flow than at the overarm port even though it comes off the 4" at the same 90 degrees. The only difference is the router port protrudes into the 4" main whereas the overarm port is flush with the main. I'm wondering if this is the reason for the poor reviews of the overarm setup and that the overarm tee that SawStop provides should be more like what they provide for their router.
Edit: While the port at the router table dust collection box is 2.25" the port for the saw overarm is actually 1.5".