I don't know if there's any data hook point in registration process... In 3.1.X there wasn't so I replaced the whole function and this is not very recommended to do.
I'll take a look but if there isn't a hook point in 3.2 or some other way to make it, I won't update it.
Hey, Maxxius, I don't use 3.0.X for ages... I won't support this hook (IP.Board 3.0.X) anymore, not even IPS does. If you're using this in 3.1.X, that can be the problem.
I will update it... If I have some time today, I'll install IP.T 2.0.0 and will try, if it already doesn't have some hook like that on Tracker package.
It's hardcoded. Open files that begins with sos31_othersgroups_global_***.php and sos31_othersgroups_profiles_***.php in your hooks folder and search for Others.