I've done a lot of research about carseats- we have a 98 S70 GLT and a 96 855R.

Neither has the LATCH system. I've never heard of the ISOFIX. My understanding of the LATCH system is that it is an attempt to avoid poorly installed carseats. The stats suggest as many as 80% of the carseats on the road today are improperly installed.

In the S70, I used a Britax Freeway. The tether bolt/hanger is installed in the trunk, under the rear deck, and the rear tether goes around the center headrest. I always use the center rear seat position, but we only have one child. The seat belt has a small switch on the back of the part on the belt that will allow the belt to remain tensioned with a car seat installation. It works fine, but I back it up with a locking clip supplied by the seat manufacturer anyway, as it will lose tension over time.

The 855 is a new (to me) car, and for that I bought a used (I know) Priori Cosi seat. I think it's a better product than the Britax, but it's not been tested in the US. It has, however, been tested in Europe, where the standards are higher, and include rear and side impact test data, unlike the US standards. The tether screws into the seatback.

Here is the most important part (my opinion) of a seat installation:

Make It Tight and Secure!

The best way to do this is to install the seat loosely according to the manufacturers installation instructions (READ THEM!) to place the car's belts in the proper places and buckle the seatbelts loosely. Then, have the heaviest member of your family place one knee in the seat where you childs butt will be, and kneel hard, pushing the seat down into the car's seat, all weight on the one knee. At the same time, tighten the car's belts. If done correctly, the seat will NOT move side to side without huge efforts. It really is strong and solid.

Oops- the kids waking up. Gotta run, hope I've helped!

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