after my visit to a local machine shop (in the back of some ones yard) I found the cost of cutting my 10mm copper down to 3mm was more than some new 3mm copper so i orded it and will get it later today. Its 50mm x 1m i think so i only have to make 1 cut each time.
the shop had a cnc machine (handy to know) and costed maching the copper base and acrylic top with just the cups , tube holes (no tubes they coudnt do anything that small) and screw holes. I would then finish the blocks my self But at £50 per unit i cant afford it at the moment after all the tools bought. besided i could buy a cascade at that price.
dont think it matters anyway i am getting better at drilling the cups and top anyway.
My idea of starting with a 1.5mm first works. I also found that if i make the 1.5mm tube holes in the acrylic first and then screw it to the copper to make the first marks into the copper i get very good results.
As i have bigger cups covering a larger area i dont want the outer corner cups to suffer from lower water velocity so i have changed the cup array to a rounder shaped with a width of 20mm.
the cups are still 2.5mm spaced 3mm apart. As i will have 3mm copper plan to make the cups 2.5mm deep wth flat bottom.