He is member number 177 of the NKC (Nederlandse Kubus Club, or Dutch Cube Club in English).
His profile in the Directory of Puzzle Collectors & Puzzle Sellers (2007 edition) notes he is the author of the book "Bandaged Cubes", and many articles in the CFF, as well as co-author and contributor to books of the Slocum Puzzle Foundation.
In fact, he recently authored an article in CFF 74, and I believe possibly one in CFF 75 (it is at home, so I can't check).
P.S. As president of the NKC Geert Hellings could probably tell us more. If you aren't yet a member of the NKC, you should be!