In my own case I can rarely find a shop with a bike (size) I am interested in, in stock or even available within a driving distance nearby. I ride 58+ according to geometry.
As you mention you can rule out a lot of bikes simply by riding. Even so much as "this is comfortable but could be bigger/smaller" and such as that. With that said I would think that a 15 min ride that didn't point out a fatal flaw is within things that can be rectified with stems, seats, and setup.