-- nickgreenberg
How would you mount the perforated aluminum to your rails? There's no guarantee that any of the holes will line up or be big enough to pass the threads of a screw through.
I wouldn't use sheers as they will probably curl your aluminum. Sheers (aircraft sheers are best) only make sense for rough cuts in my opinion. I'd use a small hacksaw. You can clean up your cuts using a deburring tool. Just do a search on Amazon for one.
-- Ronin1973
If using perforated aluminium:
You would have to Buy some Round Needle Files to open out or Slot the appropriate perforations.
Snips - Yeah bad idea, as said it will curl the metal, especially so with small parts like this.
Hacksaw - you are going to have to be very careful and accurate or it will look like a dogs dinner, you need a large Flat File rather than a deburring tool, to smooth and straighten the edges. You may also find you will need a Bench Vice to you can appropriately hold the piece of metal so you can square off and make parallel.
Personally, I'd just wait and buy something made by someone else, Eurorack looks nice and I wouldn't spoil it by making something in my garage that would look like a bag of Sh**..... I'm a Mechanical Engineer (for years, before I was a brewer).
If you want to get technical, the Aluminium Blanks from Thonk - You can see the sheer and break-away on the edges, this shows its been stamped out, the initial stampings (Holes & Outside edge) will bend the material, a subsequent stage of the Power-Press will planish (Flatten) the Blank, there will still be sharp edges so I could guess the parts are then tumbled or shot blasted to de-burr. I literally used to make the tools that made things like this.
Enjoy your spare HP, don't rush to fill every last space, this is not like filling sticker books. Resist the urge to 'complete' your rack, its never complete so just relax.