I agree with Angel, the patient has to do most of the work.
However, i would be wary of too much T/S extension. I have taken to using a digital camera on my patients to show them what their "ideal" posture (according to them) is like and then giving them ***thoracic kyphosis*** to show them what it does - a lot of my FHP patients are actually in T/S lordosis or flat backed.
The tape for T/S extension might be a good cue for them to do the exercises because as Angel said, floppy patients (excessive kyphosis) is also bad.
I think a lot people grow up with the shoulders back idea of good posture but never do it (being children and teenagers has something to do with it!). Then they get older and start to care so they try to correct it and over-correct into excessive extension.
I have had one patient who went too far into flexion - but i hadn't seen her for something like 2 years and she had no probs during that time after nearly constant back and neck pain for years! The body is a crazy thing...
BTW, i also use a digital camera because i think even our own perceptions of what is good posture can be skewed - have you ever been on a physio course where *no-one* was sore or had bad posture? HAHAHAHAHA :lol