Panic
Love the train track analogy.
Someone correct me if I'm wrong (on any of this). The goal of any header is to flow the exhaust better; to achieve more laminar flow and less turbulent flow.
Assuming your running the engine at the maximum operating RPM:
The volume and rate of exhaust at the siamese port for every exhaust valve opening event is always the same as at a non siamese port - correct? Therefore the same size pipes should be used at all exhaust ports. I believe the determination of optimal collector size is based on elimination of turbulent flow (3 trains on the same track running end to end - 'bump drafting' with no gaps in between)
Radar, there should never be any two cylinders at maximum exhaust flow rate at the same time (other than minorly from cam overlap).
