Matt - The fact you had nerve enough to ask the question means it will work for you. You understand the Magic of Gaffers Tape. Seriously, I held a Anni board up to the front standard of a Crown, and while it will take careful taping, I don't see why it won't work. The back of the Anni board comes up against the screws that hold the lens board clips on the Crown, so the lens focus plane may not be absolutely parallel with the GG plane, but it is probably close enough if you are stopped down a bit. Do a flashlight test for light leaks, of course, then shoot away.
If you want to have fun, post a similar question on one of the Leica forums - "I want test a screw mount lens on my M3 and don't have an adapter. Can I gaffers tape it on?".