Quick question for techs: Safe to use Roundabout in these circumstances?

We are traveling by plane tomorrow, and I'd love NOT to drag my Marathon for my older son. We have an extra Roundabout which we could use. He is 38-39 lbs. but is 41 inches. I checked him in the seat today, and his head is above the top of the seat but his ears are definitely below.

Is this okay then?

Thanks,
Lisa

Lisa, where are his shoulders in relation to the top harness slots? DS1 fit into his RA until he was about 42" tall because he was mostly leg.

Will you be driving at your destination, or is this just for airplane use? If it is just for airplane use, I'd probably be inclined to give myself a little more leeway fit-wise, ya know?

Have fun!!