Well, when it comes to gearing, look back to the greats in cycling history. In 1956 Ray Booty, "the boot", was the first man to break 4 hours in a 100 mile TT. His record of 3 hrs 53min 28 sec, stood for 34 years.
As was the custom for many english riders back in the day, he rode his bike to the race on the previous day....a 100 miles.
25+ mph for 4 hours. What was his gearing?, 84inch fixed, or equivalent to a 50x16.