In reply to Makeithappen:
I cycled the CA solo back in 2015. However you do it, just make sure you go. It is awesome. As others have said, I can highly recommend continuing on to El Chalten via the seasonal border crossing (walk/cycle only - no cars) and beyond if time allows.
O'Higgins is quite small so suspect you may struggle for car hire arrangements. A compromise could be to rent from PM to Coyhaique and then hitch hike the rest of the way (used to be super easy).
Other option which would be really fun is to hire touring / off road motorbikes which might give you more flexibility.
Enjoy!