ORIGINAL: Avaiojet
The twin you suggest is, most likely, wider at the head, than a single cylinder engine. The engine will also be inverted. So now I have two cylinders to deal with and not one.
That's my impression as well. It's too bad it wasn't done as an inline. Also I've heard that it doesn't provide at much power as other 200 size engines. It looks totally cool but it probably more hassle than it's worth.
I haven't seen many YS engines at the field.