Thanks for the kind words everyone! Daf - I knew you'd like this one. The one negative is that this was pretty much my exact build plan for the yellow Mooney. I don't know what to do with it now. Maybe an IGH path racer
I'll send him a line and will provide better photos of the derailleur today. It never really occurred to me that the saddle was anything special. I was just looking forward to trying an older model that I hadn't come across before.
Needless to say, I do not regret picking this up (worth driving to Maryland).