Barbara Benagh's reply:
Though I am not sure what you mean by Half Shoulderstand, breast size can interfere with all the Shoulderstand variations. The simple solution to your dilemma is to wear a very sturdy sports bra when you practice yoga. Of course, you will sacrifice comfort for this additional support, so this may not be an option if you can't stand being confined.
Your bra size indicates that while you are well endowed you are not a large woman. I encourage you to actively lift your rib cage off the throat while practicing Sarvangasana (Shoulderstand). As I instruct in my November 2001 Asana column on Sarvangasana in Yoga Journal, your primary support in this pose comes from this upward movement. If your lower ribs are caving in, your entire pose will weaken.
One of the great lessons of yoga is that the practice is subjective. As your practice matures, you understand what type of practice is most suitable for you and how certain poses affect you. Sometimes this insight includes realizing that particular asanas must be modified or abandoned altogether. If you cannot find the strength to lift your rib cage off of the throat in Shoulderstand (and breathe at the same time), some modification may be called for.
Rather than advising you to abandon Shoulderstand, I suggest you experiment with modifications. First, try placing several blankets on the floor under your arms and shoulders while you are in the pose. Try doing the pose with your hips angled back over your elbows more than your shoulders, and even put some support under your hips. Consult a certified Iyengar method teacher for help with these props.
Be assured that though your Shoulderstand may need to be modified, you will receive the benefits of the pose, such as improved circulation and more efficient digestion and elimination. Persevere, and you'll profit from figuring out a way to practice this fabulous pose.
Barbara Benagh, YJ's 2001 Asana columnist, founded the Yoga Studio in Boston in 1981 and teaches seminars nationwide. Currently, Barbara is writing a yoga workbook for asthmatics and can be reached at www.yogastudio.org.