Here's the pic I posted in post 9.
http://www.bob2000.com/acccheck.jpg
Do you see the blind hole at 11 o'clock in the right hand bowl?
That's where the pump chamber vent used to be, but obviously Holley isn't doing it anymore.
The rubbish on the other forum would do nothing if the hole is there as he claims.
Both of the holes under the umbrella are inlets to the pump chamber.
Cutting a groove joining a .013 hole to a .100 hole just going to reduce pump shot further than what you already have since more will bleed back to bowl.
The size of the bleed is a balancing act. No bleed gives full pump shot but no venting. I probably wouldn't exceed .020.