Any smoothing you do will give some results. Whther or not it's enough when combined with other mods to make a feelable difference is anyone's guess. But - you won't hurt anything by leaving a larger hole there. It does add a small amount of volume to the port itself, but like Kid mentioned - these heads are so bad that it takes a lot to make them good. It's just reality - not bashing. If you really want to "fix it right" then have the holes welded up and reshape the bowl. This will require the entire head be rebuilt because of the heating required and the distortion - but if that's also part of the plan then welding isn't a big expense. I also don't think it will give you much better performance so the cost vs reward issue comes into play there too.
