Join Date: Mar 2017
Location: Northern New England
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Photo Submissions 21 Times in 21 Posts
Marni, I think, although others here may have more info, the problem with putting a small dog in a harness is the forces exerted on the dog in the event of an accident. The harness may hold them on the seat but they may not survive or may be seriously injured by the very strong forces exerted on them. That's why they have a minimum weight.
This is the video of the crash test for the sleepy pod harness done by the Center for Pet Safety. It gives some sense of the force the test dog experiences.
If anyone has more info, I'd love to know more about this.
Note: the video will play on their website if you click on the Vimeo logo.