A 50x12 high gear is 112 gear-inches and 80 rpm will give you 27 mph and 90 rpm will give you 30 mph . Can you really ride that fast on anything but a downhill?

Years ago, the Tour de France was won on lower top gears. I remember reading Steven Roche's book where he said how happy he was to get a freewheel with a 13T small cog. Previously they only had a 14T available. That gave him a 52x13 or 108 gear-inch high gear and he won the '87 Tour using it.