I've currently got 33-18 (29er equivelent of 2:1) and can quite happily ride arround 9-10mph offroad on singetrack/fireoad with small hills for a few hours.
That gives an average cadence of ~93rpm, but that includes grinding up hills at a low cadence and coasting/pumping allong and down. So I probably rarely actualy pedal at 93rpm.
If I wanted to increace my speed to ride in a faster group would I be better trying to spin quicker on the flats in the current gear, or up the gear making climbs harder (but potentialy faster) and allowing easy pedaling on the flats?
I suspect the answer is fit a cadence computer and see how fast I actualy go before I start pumping/coasting.
drop the cog to a 17 and see how you get on?
There's not much 'flat' stuff around my way so I tend to gear for climbing effectively as everyone's fairly equal on descents but depends where you ride.