Hi Kees,
FYI this is the public Q&A forum of Kentico where mainly the community helps out, so I'm not working at Kentico!
If you want to contact Kentico directly I suggest reaching out by mail to support@kentico.com
That being said without knowledge on the technical setup it's hard to give you a proper answer. Especially since the MVC site needs to work with it.. So again I recommend to contact and challenge Aviva again as there are possibilities to support the scenario.