I've always felt unsure that the seat belt wouldn't lock if necessary since a tiny pup is much smaller than a person. I found these metal clips that keep the seat belt in place while looking for something to keep my seat belt from choking me. People in the reviews say they're like the clips they sell with baby car seats.
I'm using it with a small snoozer car seat and so far it seems much better, I was able to pull the seat belt tighter against the car seat. I haven't tried it on my seat belt yet.
The clips are heavy and smooth, they won't bend.
Here's a 4 pack for $10, I bought the 4 pack
Amazon
And a 2 pack for $8
Amazon
If you go to
http://smile.amazon.com/ you can add a charity to your amazon account and they'll get 0.5% of your purchase. Yorkie Haven Rescue is one of the available charities. You have to go to amazon smile each time though, they won't get any money from using the app or amazon.com.