So are we talking the super-double that sorrentinacoffee mentioned in the main caravel thread?
I NEED one of those, it would get me using my Caravel again. Okay maybe I was going to start using it again anyway...

sorrentinacoffee's image:

In that thread it was suggested that best results might require that the machinist/designer have an actual example in hand to match the flow characteristics of the holes.
Even then I wonder if we need some objective measure to consider, as in X amount of water passing through in X time at X pressure? The average machinist isn't necessarily going to be equipped to even measure the holes in an original, let alone figure out how to ensure that the new ones match the old ones in performance.
Aside from die-stamping, there is another possible technique which could work for the shaping of these--'spinning', which is pressure-forming a spinning disk on a lathe. It's a specialized technique and still requires the machining of a form, but the setup costs should be significantly less. Unfortunately it's labor-intensive so there are limits on how economies of scale can work out, and there would still be the problem of getting the holes done.