Is your vehicle approved as I-Size? Otherwise, it will act as a chair with isofix RE44 / 4.
The tests that the R-129 requires, can also be done voluntarily by manufacturers who do not use this approval for their devices. We know that there are many. Among them we.
The safest car seat is the center seat. If your car has an isofix central seat you can place it, but you will have to put a chair that allows it. In Spain, the average age of the mobile park is 13 years. Evaluate your cars.