I am currently saddless, too, so I'm subscribing! As far as I've researched, bareback riding is ok, if the rider's weight is average or below it, if the horse's back is sound (due to the single pressure point rider creates on the horse's spine), and if trotting, cantering, galloping and jumping bareback is not too exagerated. Also, it is said to be often that beginners tend to tensen up their seat while riding bareback, and this, naturally, affects the horse and, if the horse is on the sensitive side, it also may provoke him to be more tense and stiff than normally.