Although I've been a rebel all my life I have always rebelled within the law or the rules depending on what situation it was. Debate, demonstrations (peaceful) etc were my preferred methods. However in this case I would advocate; wrapping the banner around your person to enter the stadium, pushing it down your trouser legs to get through security, in your pocket. Or wear the hoody with the 'kangaroo pocket' as I do. I put my gloves in there and they can be bulky, never been pulled yet. I've even left my keys in there on the odd occasion, by accident, and not been pulled.
Just a few suggestions. Sorry Ric and Mods if this post is against the rules please feel free to remove it.