Do you hand engrave it, or do you do it an a CNC type?
Installed an O-ring, and doing some preliminary design leak testing.

There are many holes in the copper, but only a few in the Delrin. I am testing to see how many holes are necessary for the design. If the design is strong enough on its own, I can just omit the holes going down the channel. If there is a slight leak, then I can use those holes. Most of this is done behind the scenes but since this block didn't get a prototype phase, I am doing all the testing with this first batch.
I will likely leave all the holes since its the bottom of the block, and I can always retain the option of putting additional screws in it, should someone really put some crazy pressure through the block, then I can beef up the structure with the additional screws.
I also don't use hose clamps. I have always used a surgical rubber type hose when I watercool. It was super stretchy and never needed hose clamps. Once I see this block installed and how it works with some CPU blocks, then we can probably expand it to fit more connectors.