For anyone riding in challenging circumstances, such as moving at speed or jumping over undulating terrain, riding young or green horses etc., we would encourage the use of a well fitted  breastplate.  It ideally needs to be one that allows you to connect back to the girth straps/billets rather than the fall-down staples (sometimes called D-rings) at the front of the saddle. There are 5-point breastplates now on the market that allow you to do this, or you can use one of our own BALANCE English Hunting Breastplates.
The reason we suggest these Breastplates is because providing they are fitted correctly, they do give some extra lateral stability - they act almost like training wheels on a bicycle, not having any influence at all 99% of the time, but coming into action as an early warning system if the saddle starts to become displaced laterally in an extreme situation.