I no longer ship with cool packs. The one time the buyer requested me to use one last summer, the corals arrived in <70 degree water.
I drop off shipments at Fedex at almost 6 pm and they always arrive before 10:30 am. That whole time in transit would be just at night and morning, so it wouldn't get too hot for the corals. I've never had a problem with overheating shipments.