I'm curious. Which "Charlie"? I'll bet it's the wrong one.
Let me put it this way. If it were Charlie Schwendler, you wouldn't be on here asking questions. He makes damn sure anything he puts out will perform 100%.
In my 3x2 Flathead it was pain to change jets for primary(center), so I put those adjustable
ones in. With A/F meter adjusting was easy and it has stayed same for years. No complaints.
Your results may vary.... BTW , my opinion is that adjusting without good A/F meter is waste of time....