Using Trunki as a personal item on Spirit Air

[Aurora Belle]

Has anyone ever had success using a Trunki as a personal item on Spirit Air? The Spirit Air personal item dimensions say 16 x 14 x 12 inches and the Trunki is 18 x 12.5 x 8.5 inches. Trunki also says that it qualifies as a personal item. So do the exact dimension matter even through the total dimensions of the Trunki are smaller than the requirements? Has anyone ever had success using the Trunki as a personal item on Spirit Air? It would be so much easier to use the Trunki in the airport rather than the stroller.