We guys on the IRC channel discuss beforehand the version of WZ we would like to run before hosting a game. And since games begin in a matter of minutes from the time you're at the pre-multiplayer game menu, your chances of missing these hosted games on versions other than the stable ones are pretty high.
All you need to do is ask on the IRC games channel for people who would like to play the master testing build, and you'll find some volunteers.
"Speak when you are angry and you will make the best speech you will ever regret." -- Ambrose Bierce