I wanted to make up some stencils for the rafting company I work for that we could use to spray paint our gear. Our logo has some floating islands in it so I created some paper tabs in Illustrator to hold the islands in place. Big islands can then be held in place with piano wire used as reinforcement along the paper tabs.
For best results, you can forgo the paper tabs entirely and bend the wire into a handle shape and float the island on wires that won't even appear when you go to spray paint your image. I did this for the islands where it mattered most, like in one of the logos where it would matter most that it look clean and professional.
I found the paper tabs to be acceptable and a time saver on the letters and numbers since the eye is more accustomed to seeing stencil tabs in fonts.
More info on making floating islands in stencils can be found in Fungus Amungus' classic Stencils with Islands - Pt. 2 Instructable