The tube will unfortunately add some flow restriction though, but performance should increase dramatically, back to where it should be.
The pressure drop comes from two points: the transition from the 1/2" tubing to the individual tubes, and the tubes themselves.
With some tuning, you can get the right length of the tubes. LeeJSmith's experiments, with Cathar's posted graph pretty much show how to do it.
The design really is the best that we can do, but it's infinitely difficult to tune it right. I can't even imagine how many hours Cathar spent trying out different variations, and testing each one multiple times.
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