how much air does this little piston breathe anyway? If I had a balloon, I'd inflate it with my exhaust to see.
Duh, I don't need no stinking balloon...
To give your mod a bit more significance (if that is at all possible), I realized that I don't need a balloon to figure this out. We have the displacement (of 249 cc).
At an average RPM of 6000 (probably ~60mph/100kph) we have 3000 air-intakes...of ~249cc each. That's an impressive 12.5 liter per second! For comparison, an average human lung holds between 5 and 6 liter. To breathe in a full lung in one half of one second, I need a decent mouth opening. The nose alone can't do it.
I don't know how big, in comparison, the stock orifice in the air box is. Would you happen to know, Mike, after you've been operating in there?
All that said, at idle and acceleration from a stop, the PRMs are quite below 6K. So there, the situation is not as demanding, which would suggest that the benefit of a larger orifice is not as significant there.