Here's my thread contribution with my pooches. We're still in the "experimental familiarization phase," but the rig is already setup for canine safety. The red Australian Shepherd is going on 3yrs of age now. She was the one I was worried about sitting and staying in the sidecar because she is such a hyper, crazy dog ("high energy" doesn't even begin to describe her.).
The other test subject is my younger (16 month) Newfoundland/Bernese-mix. He's a bit more mellow, and at a 100-plus pounds (and growing)--and the size and resemblance of a small cow--he would look very handsome in the rig. Problem being....despite sitting (backward) in the sidecar photo where I nearly strained my back, the dog won't get in the tub even with treats (and he loves his treats!). He's afraid of everything.
Meanwhile, the Aussie jumps in readily and is ready to go. Test rides around the neighborhood confirmed that my brave, red-headed girl is an easy convert to sidecar transportation. And now we order the doggles.