I had an experience with a friend's horse that scrambled, then went down in
my two horse trailer. After unloading, we travelled the two horses without
the divider.
I haven't used a divider since, whether carrying one or two horses. The
horse that scrambled was fine after removing the divider.
The only advantage I have found with a divider is that you can hang saddles
and rugs, etc. on it. That's all.
My horses travel fine without it.
Luke