I've been told that small dogs' joints tend to mature earlier than large dogs'. Since yours will be 18 months old by next spring, she should be OK as long as you work on conditioning (start very slow and work up) starting about her 1st birthday. Double check this with your vet, though.

If she were a large dog, such as a Labrador, you'd want to wait until after the 2nd birthday for a strenuous trip.

I've always used a tent, not a hammock, so have no idea what to suggest.