Sorry for taking so long to reply, been busy.
Basically
Althornin is correct, u will be getting a fair amount of laminar flow. The boundary layer isnt churned up enough.
Some quick and dirty CFD analysis shows that.
The exact internal dimensions were used for the areas actually in contact with the water
A close up of the cups area
You can see that around the cups, you arnt getting much flow, the water has pretty much formed a thick boundary layer.
Anyhow, it was something to try.
As to copper, I'll be moving back to Singapore in a month, and its a lot cheaper to purchase there than it is here in Sydney, so I'll be using it over there. And since I have free access to alu sheets here in the Aero workshop, I use that instead. I did use a centrepunch, however, on my first drill, I set the drill press to too fast a speed and it went a bit awry even with a G-clamp holdin the piece down.