I agree--the crumple zone is a huge factor for me. That's why my dogs ride in the back seat where they are protected by the structure of the car. I use the Roadie seat belts by Ruff Rider. I have two of the older style, and one in the new style. The new style is just fine and I like not having to mess with attaching the two parts.
As for the video that makes it look like harnesses don't work, keep in mind that it had more to do with the style of that harness. It failed at the place where it clipped to the car. Roadies don't have clips. They have loops that you put the car's own seat belt through. Since the harness is tested to be as strong or stronger than the car's seat belt, failure is almost impossible.
Kathy Thacher (in case my auto-signature doesn't work)