If you don't pattern, you are just guessing. My current barrels handle 24g loads wonderfully well, even the .019" choke. My last gun didn't. Patterns were like Jerry P's. So what does that tell you about your gun? A half hour spent patterning will answer your question.
Tightning the choke probably will just make the pattern worse (more holes). See http://www.shootingbunker.com/OpenItUp.html for an example. Schroll to the bottom of the page.
As Goatskin says, less shot less fringe. If you center the pattern every time, the target will break. Most of us need those fringe pellets a couple of times out of each 100; we want all the fringe we can get.