/3/ - 3DCG

>>707062
In this situation i would honestly just treat it as a male chest during the skinning phase, if you are going to simulate the tiddy there is really no reason to create a system to move it yet, just focus on making all of the deformations work properly.
Also, if i understood the image correctly, there are two joints for the chest, i would remove one of them, if you look at the mirror you will see that the part where your tits/lungs are don't bend too much, but if you really want it to bend for added realism make sure to use it veery sparingly for minor movements.
hope i understood the question :3