[Fedora-spins] Adding default user to a group

Is there a way to add the first created user to a group. I have been able to add the liveuser to the audio and jackuser groups (which makes sense for an audio spin), but I have not found a way of making the user created after install (on firstboot) to said groups. Is this at all possible, and if so, are there any hint you can give me? -- Jørn Lomax GSoC atudent, Fedora audio Spin CS Student University of Tromsø