Swimmer,
The most dangerous thing (after the millions of staples) is that the structure may collapse on you when things are removed. To date, I have three friends that got injured this way. One of these even collapsed with the rear wall still in place. The other two had both ends open. One had been braced by a pair of 2*4s in the middle, but someone kicked one loose and down it went.
All these cases, be sure to have a camera man, you could get the 10,000$ on America's stupidest people....
Sorry, you are in Sudbury, well maybe there is Canadian version.
Whatever, just keep thinking what can go wrong.
Matt