Don't forget stem angle when adjusting bar height. Adding spacers is not the only option. I need no spacers with a -17 stem. Changing to a -6 raises the bars by 2cm. Flipping that stem to a +6 would add another 2cm. The flipped up stem isn't real pretty, but I now see some top level aerodynamic frames with one piece bar/stem combinations with a substantial upward rise being used in this year's tour.