I've never travelled Pickle in a trailer, as he is so big that I just think he's more comfortable in a lorry. I a lorry I use one of those ties with a quick release onto half piece of bailer twine.
If I travel my horse on her own I dont tie up at all. If she has company then she gets tied up short so no fighting as she likes the taste of fresh blood !!!!!!!!
Same as suzy - mine is in a trailer with no partitions so I cross tie to prevent him from turning around (which he did once when I'd only clipped on one of the ropes temporarily