I don't want to put a damper on anyone's ambitions, but this sort of thing can be incredably dangerous.
The rib cage expands to accommodate the organs it protects.
This sort of thing should never be considered for anyone much past their teens. That isn't to recommend it for teenagers. But past teens, and your bones and organs have more or less set.
Whatever you do, take it slowly. Don't try to tighten things too much. Gradual.
If you get any sort of discomfort, difficulities breathing, heart pumping, sickness or nausia, them loosen off quickly.
I somehow don't think the biggest problem will be the chest, it will be the shoulders.