It all depends on where the trailer axles are located, and this will vary from brand to brand and even different models within the same company. If the axles are located well to the rear, you may be able to load a single horse in the aft stall. If the axles are located under the front stall, a single rear located horse may unload the hitch.

As was stated, the best way is to first try towing the empty trailer to get a feeling of an acceptable tongue weight, and test how well it tracks and corners at different speeds. Load a single horse in the front stall and again follow your original route and speeds. You will probably notice a difference in how the back end of the truck feels, as compared to when towing with the empty trailer. Move the horse to the aft stall and try your trip again, BUT more slowly and deliberately. You may notice some swaying when coming out of a corner or when traveling at highway speeds. Immediately slow down if any swaying happens and reposition your horse to the front stall. If swaying occurs, you will not be able to carry a single horse in the aft stall, without more weight in the dressing room. With a horse in the aft stall, you will have to counter weight the front, with enough weight to at least equal the original hitch weight when the trailer was empty.