Default usergroup and group quotas

Hi everyone.
Does anybody use the functionality of group quota's?
We've met the following problem: when you create or edit a user, by default it goes to OMV_USERMGMT_DEFAULT_GROUP (users, gid 100). All the groups you choose in web interface are secondary groups. It's ok, till you need to use group based quotas, since they work with primary user group. It's possible to run usermod manually, but it seems to me that I'm doing something wrong and this functionality should work fine...