A Photo Blog
The drop out configuration looks awfully suspect to me. That and the odd profile seat tube make me wonder. Yoshi certainly wasn't afraid of playing with unusual frame designs, but this doesn't seem like his style. Weird.
That's my feelings too....I can't find anything close to this design in any of his frames...but as you said, he wasn't afraid to experiment
I'll bet it's authentic. Looks to me like a bike Yoshi built for a trade show. He always had something a little on the wild side at the shows. I bought several from him at Interbike.