^^^^^^ +1
20 gear inches is = to about a 34-46 crank to cog ratio. I would not find this serviceable unless it was for extreme ascents for short pitches. Too much aerobic and not enough strength for me. 1:1 ratio in a 34:34 setup gets me up every ascent without overburdening my aerobic system. I am 6'2" 210 lbs and my cadence is between 60-80 depending on the gradient and length. Spinning at 90+ rpm up grades is not my preference.