You didn't mention where you're located at, it's important. Although the recommended sizes seem reasonable and close, how would you know without the posters barometric pressure and temperature? The other poster might be at sealevel, and hot. You might be at a different altitude, and cold. An Air density reading is how you tell the difference. A 1% change in air density calls for a 1% change in jetting. With the jet recommended, a .039", if the air density changes 1%, you have to change the whole size 1%. In this case 1% change in air density calls for a .0002" change in hole size. That's right at 1%. Some of this information was taken off the Longacre website.
It's called tuning, and tuning is tough. (Al Nunley)