Associating multiple OpenID's to a single user using the built in ASP.NET providers

Question

I've configured a new MVC2 site to use JanRain Engage (formerly RPXNow) for authentication.

I would like to be able to associate multiple OpenID's to a single user account, but still use the built in providers.

Is there a good solution for handling this without creating new tables or heavy modification to the built-in stored procs?

Potential solution (comments wanted):

I was thinking about storing the OpenID identifiers in the Profile table, I can then find the user account by first looking there then passing back the associated user.