I hit 40mph+ on a steep downhill towards my house. That's about 200rpm with 48x17. Pretty fun. The trick to not bouncing is to concentrate on your pedal stroke. Folk'll assume that riding a fixie will give you a perfect pedal stroke, but that's not necessarily true. You have to focus on staying "on top" of your gear, as in, applying an even amount of pressure across the whole rotation, rather than just pushing and/or pulling.

Spinning 160-180 for a short amount of time isn't that nuts, though. Most sprints happen at something between 135-145 for longer period sprints, and 155-165 for short period.