I owned a set briefly, bought from "Campervan-bits".
They arrived in the wrong colour, and 3 rail instead of 2, but the most significant issue was that the two outer rail opening centres were 1.5cm different from the floor/seat rail centres (narrower).
This resulted in the carpet being "lifted" by the floor rail near the sliding door.
That created a gap and trip hazard, and also meant that the velcro contact strip by the door did not engage at all.
Campervan bits were superb in following up, and confirmed that this was the second similar observation he had had in two weeks.
They went back to Brandrup, who indicated that the rails must be incorrectly installed in my new 6.1 Ocean.
Their carpets were absolutely manufactured to a quality standard and could not be incorrect.
And they are great quality, but just didn't fit my California, so I couldn't use them.
I asked VW to confirm that the outer rail spacing was the same for both 2 and 3 rail vehicles, and of course they are.
They don't rejig the floor just to fit the third rail.
I was amused at that thought that VW adjusted their seat fixings and floor pans to match different rail centres.
So fine, they got them back, and I received a full refund from Campervan Bits, who were professional and superb throughout-as I already mentioned.
What I did next was to go and buy some rubber backed heavy duty carpet/office tiles in the colour that I wanted, and stuck them down on the original "wooden" floor with double sided sticky tape.
They are lightweight, tightly fitted and waterproof (with joints virtually undetectable), and can be fitted easily using some waxed paper or cardboard to make a template, and then cut out with scissors.
Most of them go down as full tiles anyway...
Took about 3 hours to do the whole van to the back door in the living area, and they are super durable and tightly located. Been in about 3 months now, and have been perfect throughout.
I also bought some VW rubber matts for the driver/passenger foot wells-then filled the section in-between with tiles too.
They are also thinner than the Brandrup carpets and so the seats slide/move unhindered.
Any spillages, just remove and wash the tile, or replace it.
They look great and cost about £80 for the lot.
Nice thing is that they don't slip, and can be removed at any time with no marks to the original flooring.
As they are not removable in one piece for cleaning (in the way that the Brandrup can be), I also bought a £30 12V hoover...
Just a solution which works for me, and it might be useful to think about.