I'll link to my album with 2 passive ways using gravity to stretch that work very well for me.. suggested by a teacher of PT that also helped me a lot by doing a top rib mobilisation for me.. It was a great help and no other PT or chiro had mentioned or tried that.. Chiro did do rib mobs after I mentioned how much better I felt after that first time..

http://neurotalk.psychcentral.com/album.php?albumid=422