Update again.
What you are looking at here is a 1/2" T fitting and a 1/2" to 2 x 3/8" T fitting. The ID of the 3/8" section didn't impress me much at all with cross section of 19.6mm² compared to 58mm² for the 1/2" section.
The plan was to use 3/8" in parallell for the array blocks but with the flowkiller above changed those plans.
The second block has been assembled and cleaned up. Here we have a test fit to try out the screws I after a lot of issue got hold of and to see how much that has to be cut away on the 1/2" barbs to make them fit properly.
Barbs trimmed and installed with silicone adhesive. The 3/8" Tygon was a challenge to get over the 1/2" barbs but they got there in the end.
An unexpected issue occured, all the tubescrossing over each other ended up too thick to make the array fit in the right direction. And where the barbs now are is not a good option... Back to the drawing board.
Ok, a quick fix, let's put the blocks in series instead using 1/2" tube. As I wrote above the cross section in a 1/2" barb is 58mm², well the cross secton of the channels inside the array blocks are 54mm² so no major loss of flow. Actually I wonder if it even can be noticed with a Swiftech Storm in the loop.
New attempt and this time the array did fit in the correct position...