Yeah just be very careful. If you're not in Qantas mainline then you won't be covered by the PIA, so theoretically they can hang you out to dry if you get caught doing anything which could be construed as industrial action. This can basically be anything which is different from your "normal" routine.
However non-AIPA members who are in Qantas mainline are covered by the PIA, as long as they individually notify the company of their intent to participate.