Accessing custom values + custom registration on signup

We want to access custom values (CV1 etc.) and custom registration fields programmatically when a user registers on the site.
Is the ws_plugin__s2member_during_configure_user_registration hook the best place to do this?
What index do I need into the vars array to access:
1. The CV values (is it just $vars['cv1']) ?
2. Custom registration fields (is it just $vars['fieldID]?
Thanks, Roger
Is the ws_plugin__s2member_during_configure_user_registration hook the best place to do this?
What index do I need into the vars array to access:
1. The CV values (is it just $vars['cv1']) ?
2. Custom registration fields (is it just $vars['fieldID]?
Thanks, Roger