>I do believe you can get shoulder in/out with the bitless bridle.
Although dressage is NOT my forte I just had a gal that did very well
competing in the dressage ring ride my husbands second level dressage
horse, with a rope halter. (Since he is new to us, I wanted to see what
he knew)
She was doing shoulder in shoulder out, extended trot, collected trot,
and leg yeilds no problem. He looked awesome! I have ridden this horse,
and he seemed dull. As soon as she rode him and was pushing all the
right buttons (aides applied correctly that he knew). He was wonderful.
Since he was not wearring a bit, I guess she didn't need one to get him
to respond.
My own mare that was strated bitless, does move her shoulder out when I
hold pressure on my inside rein, and slightly cue her with my inside
leg, so I say the anwser is yes.

You are going to hear many people say "How can you get them "on the bit,
when there is no bit" You get then "on the aids" it looks the same,
actually it looks better!