Just a "report" after taking dd to the zoo today in the Trekker. She fell asleep on the way to the zoo, and once she's out, she's out for awhile (must have been from slinging her and her napping on the go from birth). So when we got there I set up the Trekker on the back seat, then lifted her out of her carseat and on the Trekker, secured the belt, and then slipped the shoulder straps on. Amazingly she stayed asleep! I set her way down so she was practically sitting on the belt, so the back of the Trekker was about at her shoulder blades. She slept soundly while I walked around the zoo and woke up about 30 minutes later.
So yes, they can sleep comfortably in the back position. Her head was resting on my back. I had the pocket stuffed with a diaper change, wipes, a sippy cup, and my wallet and keys, so no extra bag to carry. :-)
BTW I saw a dad wearing a Didymos!! It was pretty but I think the Trekker was a whole lot easier to put on from the looks of the way it was all tied up. I'm sure he had help getting the baby on.
7yo: "Mom,I know which man is on a quarter and which on is on a nickel. They both have ponytails, but one man has a collar and the other man is naked. The naked man was our first president."