Your server-side script, sSelectList2 need to be incorporated in your client-side script as it need be executed once the client has made a selection. If you have a default value, then the same code that populate your drop-down list should be used and be executed after the page loaded.
That ensure the drop-down population is always done the same way.
Server-side scripts, those shown under the Scripts panel in the Designer are executed in the Connect Server while building the web page but are no longer accessible once the page is loaded up in a browser.
On the other hand, it is through a server-side script that you will put the content of your data model in your hidden field to access it at a later time. Something like this:
Selector: <your selector>
results.attr('value', record.fields.<the field>);
Then your client-side script can look into that value and populate your drop-down on the fly in the radio button event.