There was a half mile stretch averaging 12% that I did last week on 34/32 at 5 mph, never felt close to needing to unclip although I wouldn't say that was spinning. You can easily get 1:1 ratio these days on a road bike without much hassle, although it's better to start with a compact chainset because then there isn't much you'd need to do for a medium cage RD to accommodate the max rear sprocket.