I was just looking at an advert for a back brace on FB which forces the rider into good posture and I can understand the appeal.
So many riders suffer from poor posture, why wouldn't you want to wear something that corrects it - a quick fix?
Well, because anything that forces a 'correct' appearance is superficial, short-term and potentially harmful.
I work with people all the time who are striving for what they think is good posture but are really just adding masses of tension onto a system already overloaded with a lifetime of bad habits.
IMO it is much better, safer and thorough to learn to UNDO the habits which made your posture bad in the first place.
Then you can achieve your goal with comfort and lightness. Your new habits will be effortless and long-lasting. And also you won't be loading even more stressy, confusing signals on to your poor, sensitive horse!!!!!!
Come and have a free taster lesson with me and see how good it feels to get good posture naturally