i would prefer to use a screen for that piece than a nug to block it. if the screens are too big, good, if they are metal screens. First, i like to use the gold plated steel screens, unless its a regular bowl where the nug plug would work, i would use glass screens.

But yours seems like a job for metal ones. and when you want it to fit right, you place it over the top of the bowl, like a hat almost, flat though. and then with the finger that would fit in the hole, like a pinky or pointer finger, push it down, so it makes a kinda semi-circle that wraps around your finger as it goes deeper, then when it is deep enough, remove finger, and screen should stay in place, and is removable with tweezers, paper clips, toothpicks. It may not want to stay in when it is so clean. But if you smoke right after and dont loose the screen the res will hold it in place after that and you can turn your bowl this way and that.