Any sport boot is too hot for shipping. Your horses legs are going to over heat and its not pretty, it can cause long term damage.
Those who use wraps for long hauls, keep in mind the same thing can happen. Legs can over heat. Also they will start to slip. Most shipping companies do not allow any wraps for long hauls, especially over night. If you are worried about protection for long hauls and don't want boots(which btw are much better for long hauls) use just bell boots.
I love shipping boots but I will only use the ones that are the stiff ones and cover hocks and knees and have the rubber liner at the bottom around the ball of the heel.
Whatever you use, make sure you put tape over the velcro.