catamarans & windvanes
The folks at Scanmar International that sell monitor vanes seem to think that it works OK. I cannot understand how, for example, having the vane on the stbd hull on a close-hauled port tack would work. Seems like the vane would be in a big windshadow. When I spoke to them at the Oakland boat show last year, they seemed convinced that they would work, and had customers who used them.
I suggest contacting them for their opinion. They are very knowledgeable and have sold thousands of vanes over the years.