I have sat for few times on -not schoolmaster dressage horse, but horse with ST grade in both dressage and jumping (we have Z-L-S-ST-T-TT grades). It was nice experience, because it was opposite to the horse I had been riding in that stable-Niel was hard to push even to trot, he was not able to do leq yield, or shoulder in, or to canter on circle under saddle. Just schooling horse. He was absolutely reliable, you could shoot next to him and he will just look what's disturbing him from eating. But it was bad for me as "later beginner"-I was supposed to learn correct aids but he was ridden mostly by mouth. And when I sat on Fin? I didn't have to use reins at all. But if I kicked him too hard, or got out of the balance, he just got me down without any debate
If I turned him with reins, he got me down, on the other hadn, while I was balanced, didn't disturb him in mouth, didn't kick him, he was w/t/c absolutely perfectly...
For me it really was something. I think it's good at least from tim to time to sit on some qalified horse, which will teach you not to be too hard as you are used to be on school horses...
I am grateful to Niel that he tought me how to sit and to be sure in w/t/c, but really, he didn't have anything to teach me then and since I really desired to ride him still, I just sat from time to time on some experienced horse. Because from Niel I had too much bad habits-turning with too much reins, halting with too much reins, too kicking in aids (-->uneasy legs and seat generally, heels up,...) and these horses put me back to normal
>>of course I rode him with one-bit bridle