Drilling holes works well, better than making the disc mesh, it's fine if you can get the right sizing, but the drilling of a pre made impeller is very easy, and it fits well and do not reduce the flow nearly as much.

I do not like disc diffusers as they are inconsistent and have sometimes a lot of backpressure, even the ADA, so on one tank, the CO2 does not start or finish for 1-2 hours.

Unless I use a timer separate for the solenoid, I cannot get the right CO2 at the right time.

So I have issues with the disc as much as equipment inside the tank.
I have some disc that work well, but only a few.
Cleaning weekly etc did no good.

I have a couple that are decent, but I must have went through 20.

The pore size, backpressure etc, are not consistent.

Regards,
Tom Barr