I have used the drivers of Hauled Wright before they started out on there own- they hauled several horses for me over the years(when they were with another company) including a heavy in foal more from the East Coast to CA and she arrived as did all in great shape. NO problems at all!
My advice to you is this
ASK TO SEE PICS OF THE TRAILER-
ASK IF IT HAS PRE MADE FULL LENGTH DIVIDERS(especially if it is not a mini only trailer.)
I will NEVER EVER EVER had I known a company (not the one i mentioned above) hauled horses like this it would have never happened
haul my horses in a trailer where panels and twine are used to make any sort of dividers, where venalation isnt great, where groups of mares are put togther in a corral inside the trailer especially one made of panels and twine.