XJ Series 1 wheel wanted

I’m finding it more difficult every day to leave these beautiful wheels sitting in the garage instead of mounted on my XJ40, so I took a fresh look online for wheel spacers and came across a promising possibility:

Does anyone have any experience with this seller, or with this type of spacer?

They offer them in 5mm, 8mm and 10mm thickness; anyone have an idea which would work for this application?