I started with this (1" round aluminium alloy bar):
And used this (my Taig/Peatol lathe):
To produce this (a big pile of swarf):
And this (the heater fitting):
Here it is next to one of the large aluminium pipes that came with the matrix and the rubber hose it will connect to (from this you should be able to see what I mean about the limiting factor in the heat output being the size of the old plumbing):
And here you can see how it fits into the heater matrix in place of the existing aluminium pipe:
