Same table I have. The gap is variable. I have the metal box below with 4 inch DC port in back with a Y connector to which the 2.5 inch hose from just behind the fence is attached. You can also trim off a slight 45 degrees off the bottom edge of the fence to help give the sawdust a way to get sucked away. Can never remember the word for this slight relief cut, which can easily be done with a block plane. If I were going to cut a hole in the plate, I'd make sure it was filed very smooth so it won't catch sawdust on a rough edge.
The more I do, the less I accomplish.