Forum .LRN Q&A: Is membership in subgroup but not in parent group possible?

Is it possible to give a user membership to a subgroup but not to its parent group?

I want a dotlrn_club with two subgroups, sub1 and sub2. Then grant userA and userB access to sub1 and grant userC and userD to sub2.

A fifth user, userE is a member of the parent group as well as the subgroups.

I know it can't be done with the current UI, but is it possible?

I cant see anything in the datamodel that would prohibit this.
Any advice appreciated. Thanks.

yes, indeed is possible, through acs-rels, look at dotlrn_class::add_user for do it manually, but ain't sure if it is not possible at all through the UI? I think you can add members freely from the "add member" UI.....