The header shown was a prototype. I did state that the actual product will be made different and better than that. The last collector will be made different but the collector on the end of the prototype header will not impede power by much if any at all. if you were to see it in person you would understand.
also, the cylinder pairing is important and on many 4-2-1 setups, non sequential pairing when built correctly does take advantage of scavenging more and will provide more power gains over the conventional setup dyno proven.
Last I checked I have spend hundreds of hours on the dyno building, designing headers and testing them. not just on paper specking them out, but also testing. this header is being built with all of the knowledge gained from everything else I have done.
Again the merge from the secondaries into the rear collector will be different on the final product.