Dear Maciamo,
I would have expected Belgium and Northern France (Nord, pas de Calais: Saxons, Franks, Frisians + Danes) to be around 15% and Normandy (Danes+ Franks) + Picardy (Franks) to be around 10%.
Mertens even put 20% I1 in the flemish population
Journal of Genetic Genealogy, 3(2):19-25...