Famoroso...FWIW...I too recently purchased Recaro PP ABEs through FVD Brombacher...I asked if I could go with the lighter, less involved, lower priced slider and aluminum side mount, and the techs in Germany insisted the ABEs had to be ordered with a more involved kit. The slider has the receptacle mount welded on, so no add on and washers...I thought this might be for TUV regulations, but maybe it also has to do with the length of the receptacle. Part #: 869 426.
They are not installed yet, so I can’t be sure...but I definitely recall the ABEs had larger lap belt holes to accommodate for the belt to be inside the bolster. I did see a different post a few months ago, where there was challenges with the install of these sliders (not all elements in the kit are used, so it looks a little confusing)...I’m hoping mines goes better.