It is hard to get higher than 100" gearing on a 20" wheeled bike:

406mm rim + 28mm tyre = 462mm diameter = 18.2"
gear ratio max 60T/11T = 5.45
gearing = 5.45 * 18.2" = 99"

To get higher, you have to either get a SRAM dualdrive in the back or a Schlumpf speed drive in the front.

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.