You can actually do the inverse of what my friends do for open chest binding, and it'll prevent the 'tearing off the skin' parts. First you need to buy pasties. They're plastic self-sticky bits that cover your nipples; trust me, you do NOT want to damage that part of your body. Once you've applied that use medical tape to go from the pasties up to your clavicle, or even shoulders if you want. The tape is meant to go on all sorts of skin so it won't rip into you. It's also meant to go on areas that sweat so it won't peel up as easily. All of this will give you under-boobs that shouldn't shift down; however, if you want even more security you can use the fashion tape on the outfit and stick it to the medical tape.
~I've gone to look for myself, if I should return before I get back keep me here!~
Costume list 2009: Finished
17 initially planned :: 15 completed :: 6 moved to next year
Costume list 2010: Started
6 from '09 :: 9 initially planned, now up to 22 total