It is hard to get higher than 100" gearing on a 20" wheeled bike:
But the above 99" is what I have on my Swift (see sig) and it has sufficient gearing to keep up with the lycra louts.
If this seems still too low to you, you might consider your cadence - is it to low? For details about this, see the late sheldonbrown's site.
I don't have to have a 20'' bike, that's why threw the matrix and Cadenza on that list, they are 26''. I don't know much about cadences. All I know is that when I'm going along as fast as I can go (which is what I want to do), I am spinning the pedals at a decent pace, fast enough that it feels like each stroke isn't doing very much on flat ground. It feels like to go any faster, I have to put in an exponential increase in energy and effort. This is when it's time to switch gears I thought? Who is this sheldon brown? Maybe I should read into that...
Oh, and that's a nice looking bike!
I found his site, I will do a little bit of reading, thanks!