Okay, so tell me if I'm understanding this correctly:
-a no-pull harness is used for walking, training, tieouts, etc and has a ring on the front, underneath the chin
-a harness to be used for attaching to car seats should have the ring on the rear of the harness for comfort purposes.
In other words, I need to purchase two harnesses?
On the no-pull harness, the ring is actually on the middle of the chest. Not all dogs need a no-pull harness… many learn to walk without pulling on a regular harness. But if you find that you are having a hard time getting the concept of loose leash walking across to an over-excited puppy (or dog) out in the real world, the no-pull harnesses can help a lot.
Yes, you should use a dedicated car harness in the car, if you are not going to crate your dog. The Petco harness looks like a nice all-round harness, but it is NOT a good option as a car harness, simply because it stretches. Under impact, the dog could slip right through the front of the harness. (think about it… seat belts are NOT stretchy… for a very good reason!)
Also, you do not want ANY metal hardware between in the connection between the harness and the seatbelt. This hardware is a real weak link, and has been shown to fail over and over. The safest connection between the car harness and the seat belt is a heavily sewn slot of webbing on the back of the harness, which the seat belt slides through.
A final word about dogs in the car. Your dog should NOT be in the passenger seat unless you can disable the airbag on that side. An inflating airbag can easily crush and kill a small dog in a not very severe accident.
Kodi does ride in the front seat with me, and I TOTALLY understand the attraction. He is very goo company! But my car automatically disables the airbag on the passenger seat unless there is at least 70 lbs on the seat.