To answer BlazingPedals question:

The Sofrider comes with 26 inch wheels. So this would be an increase in diameter.

Because of the popularity of 650B tires with brevet and randonneur riders, there is a good selection of high performance tires for that size. Also, I am wondering if the slightly larger tire size might change the handling "problem" in a good way.

That's why I am considering them, and why I wonder what other people's experiences are.