IMO, the chances of being pulled over in a stagea are somewhere between nill and f**k all (driving style excluded of course)
Earlier this year, we had a Ignition DVD hotspot here in Perth that got completely out of hand. It ended up in the news and started the standard cycle of "hoon" stories on ACA and TT.
I was there in my stag, and about 10pm when the burnouts started me and the missus decided to take off, just as the po po decided to close down all the entrances and do vehicle and license checks on all and sundry. I was in a cue of about 25-30 cars already trying to leave, and I was the ONLY one that got waved through without a second glance. I was kinda put out at the time, because it is my first real "performance" car, but it is all legal and i was looking forward to answering all the standard questions about mah wheelz.
Having said that, there was another WA stagea owner there, and he had to wait until about 3am before the cops took off so he could even start his up, but 600hp awkw JUN motors with bugger all mufflers will do that to you, no matter what car its in (LOL)