I have no idea about flexidiscs, but why dont you just squat a building? Read up on it, get the legal notices posted and DONT LET THE COPS IN because it's none of their business and it's not a crime. You can't be arrested, it isn't illegal and it will take them about 2 weeks to get you out, which should be plenty of time to hold your event.
Trust me, I'm a squatter.
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