XF 1.1 Mass Usergroup Change


We have been trying to integrate aMember and XenForo. We did an import of users from XF to aMember, per their instructions.

The problem is that somehow, all members in the forum are now set to the Administrative usergroup, and all secondary usergroups are cleared. I have not been able to find the link between aMember and XenForo that would change those groups, especially when someone pays for a subscription (gain access to forum), or a subscription expires (lose access to forum).

For damage control, however, we want to restore the usergroups back to at least the Registered usergroup so members can get back in normally; we will iron out the subscription issue afterward. I understand that XF doesn't have a mass usergroup change feature, but what else can I try? I have a couple of ideas:

1) Is there an add-on? I had no luck searching for one.

2) Would usergroup promotions work, even for one-time use?

3) How about a database query? I don't know which tables need to be touched to make certain the correct usergroups get assigned.