I have activated the SSO system with jsConnect addon and it is working great.
But I would like to add more custom user data (fields) in the creation of the user profile.
Is it possible ?
I really do not know, but if I were you I would try the following: use the Profile Extender plugin to create the fields you need. If they are called exactly the same as they are named in your other system, there is a chance that the rest happens automatically. But that's just a wild guess...
I'm trying to figure this out too. I basically did what @R_J suggested but now jsConnect is giving me a "Signature invalid." error when I try to login.