My bet is plugging the holes will give you to small of results to matter. Remember all flow travels though the least amount of resistance. You are talking about very tiny holes that go nowhere.
But increasing the size of the valve's port will, though you run the risk of countering the blow back force needed to recock the hammer.
I'd like to know if you elongate the bolt's valve input port so that the bolt and the valve ports match up sooner, will you get a boost? But is that removing the small shock buffer the hammer needs to not wear down against the valve?
Take out the screw plug for the valve port behind the feedblock. Then use a marker and put a matching size dot on top of your bolt right above where the bolt's valve input port is. Then manually work the action of your hammer and you will see at what point your bolt's input valve port aligns with your valve's output port. You'll feel when the hammer hits the pin and when in the depression cycle the two line up. That better explains what I'm talking about. Then measure the distance traveled when the hammer hits the pin to when the two ports just start to line up. That's the initial sock absorption buffer zone. Then measure the valve pin's lip length that allows the CO2/HPA to slip around the valve and push back the hammer. That should tell you how much you have to play with in that buffer zone.
Having the hammer slam into the valve over and over will really mess an aluminum body up over time.
You might look into getting an open faced bolt over the center fire bolt to increase FPS. It's the easiest drop-in increase for FPS I've seen. Mainly it does not restrict flow and places the full gas blast across a much larger surface area of the ball at initial contact.