Membership + Cimy User Extra Fields

I'm trying to add custom fields to the registration/profile form. I read in the forums that BuddyPress is the best to use with the Membership plugin. The thing is that I want to add upload file fields as well, and only the Cimy User Extra Fields plugin allows this. Why the extra fields added with this plugins are not showing in the register form? I can see then in the user profile, just not at inicial registration. How could I make then visible? This is the url of the plugin: http://wordpress.org/plugins/cimy-user-extra-fields/