I’ve got 20s on my t5( manual), ran them for 6ish years. No issue. Previous comment and new van being a dsg, got me thinking. My thoughts are similar, bigger wheel, smaller tyre, creates something not to dissimilar from standard wheel, maybe the weight of the new wheel could effect? Is the van going to be used for heavy loads? Could this put strain, I doubt it would be significant to do damage? I don’t know? More research to sypher through. I did ask vw sales guy, bigger wheels/ warranty. He said you should be ok…not a definitive answer by any means.