FOSUserBundle multiple user types

I am building an application where I have (at least) two different user types, let's say buyers and sellers. Each user type should have its own logic (registration form/process, profile, rights, ...) but I would like to use FOSUserBundle with each user, in order to have a common management on some points. I am actually blocked by registration forms ; it happens that I can't declare different forms into FOSUserBundle, and after some research it seems to be impossible. Some answers that I found suggests to use my own registration form, but then How to link it with FOSUserBundle ? Should I populate myself the user table in controllers/forms ? This way the different users would allextends the User from FOSUserBundle, and then I should manage the different forms myself without extending those from FOSUserBundle ? Thanks by advance