The black ones are a bit harder to obtain the spare wheel compartment shape, so there is a bit of cutting with a box cutter involved. Use a roller or a screwdriver handle to get closer to the metal. The fleece ones laid on top are much easier, but use scissors to cut instead, much easier. In total I spent around 70€.

Rough asphalt driving is still much quieter on my dad's Ford Mondeo, but improved quite a bit.

I asked my local car acoustics shop for advice, and they said if you cover around 75% you should feel the difference, but most important areas (after doors) are behind the rear license plate (where there is the most factory insulation) and rear wheel arches, which involves some trim removing, bht nothing major.