I am writing a custom app for a client that is based on BuddyPress and WordPress. One of the requirements is a custom registration form. To accomplish this, I have managed to hack a custom register.php together inside of a child theme which does the trick. The part where I am stuck, however, is getting BP to save my custom fields without hacking the core. I understand that I might be able to use the "user_register" hook to save the fields but I am not sure if that is the best way and if it is where in the database to store the custom fields. Can anyone point me in the right direction? Thanks!
P.S. I also need a second submit button that redirects to a different page than the normal one for further processing but I may be able to figure this out myself.