I have a 2017 CAAD 12 Black Inc. I added Enve Handle Bars, Reynolds Attack wheels tubeless and my saddle of preference. Mine came with the Cannondale carbon seatpost.
This bike is very, very comfortable. In the five months I have owned it I have used it for six metric centuries, three 75 mile rides, two centuries and The MS 150 in one day ride (160 miles).
I'm not as old as you but have had middle and lower back issues for years. I have improved my core strength and slowly gone from a very upright position to a very aggressive one.
The CAAD 12's come with a lot of steer tube. You can start off very upright and work your self into a riding position your fitness and preference allows.
I have worked in the industry for a long time. I have owned, ridden and demoed more bikes than I can remember. The CAAD 12 with the Cannondale carbon seatpost and carbon bars is as comfortable as any road bike other than ones with suspension or other non standard design elements.
Go CAAD 12.
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