I am going to choose a new supplier for MakerSlide tomorrow, after I have a final conversation with those on my short list. I received all the quotes I had been waiting for, and they confirmed that they could extrude 6005 aluminium alloy. 6005 is mechanically identical to the 6105 alloy used by Bart Dring in the US, but more easily available in Europe. It is stronger than the 6063 alloy commonly used for extrusion. The old supplier used 6060, which is somewhere between 6063 and 6005 in strength. 6005 costs only pennies more than 6060 and 6063, but is harder to extrude, which is why not all mills can use it for the MakerSlide profile.