Jetstar carry-on 3–4 cm too thick to Okinawa, anyone had issues?

Flying to Okinawa with Jetstar soon. My cabin suitcase exceeds the allowed thickness by about 3–4 cm, but the weight is within limits. I’m totally fine paying extra fees if needed, but online I can only find options for extra weight, not oversized cabin dimensions.

Has anyone flown Jetstar to Japan/Okinawa with a slightly oversized carry-on? Did they make you check it in, charge you at the airport, or were they flexible if it was only a few cm over?

by Kind-Pen247