The only concern that I may have is that the dat's dorsal spine may have gotten stuck in one of the holes..if that happen, it'll start an infection and massive stress on the fish.
I shipped a 12" and 14" dats before, but I used a rubbermaid tub. I placed a thick o-ring rubber between the lid and the tub lip to create a watertight seal in case the box is turned over. I taped the lid very well to make sure it stays with the tub, then plastic, then box and I shipped cargo.
It was a succesfull but it was nerve wrecking and I wouldn't risk it again honestly
stan