not sure if these requests are possible...
 

#1)
I have about 50 secondary usergroups. A registering member MUST choose only one when they register. I want the custom title of that usergroup to replace the default title... I already set them all to "override the default title" but this only occurs if the member chooses that usergroup to display over the fault in their CP. Can I have the custom title override the default title by default? (if not there should definitely be a checkbox on that page for "always override" defualt title in addition to "can" override)

#2)
Can I make it so that each member may only be a member of one secondary usergroup at a time? Should I have made those usergroups primary or custom instead of seconday/joinable to make this possible? (sorry, noob)

It would need to be set to primary groups for both to apply.