If you find your ZX12/other sportsbike a bit of a pain on the longer rides, I'd suggest one of these kits to raise the bars.
This is without a doubt the best mod I have done to my bike thus far, and will do the same to any of my successive bikes.
The one down-side, is it does make the front end a little lighter (as you're more upright+further back), so I'll be purchasing a slightly less upright bar to replace.