Mingle uses a page slug for presenting the registration page, thus overriding the default WP registration process.
The easiest way to get s2Member integrated with Mingle would seem to be to change the new member registration processing (after payment is approved via PayPal) to redirect to the Mingle registration page.
Is this a good idea, and where would I make the change in the s2Member code?
P.S. An enhancement that allowed us to add a page id for a custom registration page would be fantastic!