The free registration pro-form has an attribute for the Level you want to give the user that’s registering for free. [hilite path]Dashboard -› s2Member® -› PayPal® Pro Forms -› Shortcode Attributes -> level[/hilite]
level=”1″ Membership Level [1-4] ( or, up to the number of configured Levels ). Only valid for Forms providing Membership Level Access, which includes Free Registration Forms too. Free Registration Forms allow a value of level=”0″ whenever register=”1″ for Free Registration. In addition, Free Registration Forms will also allow visitors to register for free, even at higher Levels if you wish. Free Registration Forms will accept any value [0-4] ( or, up to the number of configured Levels ).
I hope that helps.