I know you posted this a long time ago, but I wanted to reply, just in case other women have the same question. Chriopractors often help women who have had a baby that was posterior for quite some time in labor and then end up with c-section for failure to progress. My daughter was posterior for much of my labor....at the time I didn't know much about chiro care. But the center near me has great success with helping women who'd like a vbac do it successfully. The baby's position in your womb is significantly influenced by the health of your spine and nervous system...that's where all the messages that control labor and birth travel.
I know most people only think chiro care is for turning breech babies or back pain lol...but it just ain't so. Seeing the success of the chiropractic center near me with vbac moms who've had posterior babies gives me hope :). So, it is *not* about CPD! Your pelvis is, in all likelyhood, just fine. But it may be worth your while to check out a well-respected, very experienced chiro for this. Don't be afraid to ask for their success rate - if they're really good, they'll be proud to tell you :).
P.S. Research on chiropractic care shows that it reduced labor time for 1st time moms by around 24%; for second time moms, around 39%. (Wish I'd known about chiro before my 56 hour labor that ended in c-section!!!)