Been reading plenty of posts regarding the front caliper issues and don't worry, i'm not going to ask the usual stuff.
Can i just confirm, with regard to doing a straight swap from a ZX-6R or ZZR1400, do i need Kawasaki part numbers 43080-0046-DJ (right side) & 43080-0047-DJ (left side)?
These numbers seem to tie up with both bikes from the microfiches i just looked at.
Your first mistake is considering to buy brand new OEM calipers. The calipers are awesome, but for $600, uhh no. You add a few hundred to that and you can get some bad ass Brembo mono blocks, not the shit units that come OEM from the gixxers.
Buy them used off Ebay or someone parting a bike out. You could do a total rebuild on them if you desired and still be making out.
I do not agree with the other 2 people replying about the calipers being crap. I would be willing to bet they are running complete garbage pads or did not properly scuff the rotors and they switched brake pad material type and the pads are not bedded in properly.
The caliper swap fixes the mushy lever, as ZX10 stated himself, they worked so well that the lever doesn't engage enough to even trigger the brake light.
Less lever travel is a problem? Isn't that way you did that in the first place...LOL. Get the proper brake switch from the newer M/C...problem solved.
What ZX10 and Chris_1973 are complaining about is 100%, without a doubt, directly related to brake pads. Pads control the feel and feedback on the brake system, period. What the rider prefers in a brake pad is purely preference (Progressive feel, strong initial bite, less initial bite, etc) , so there is no one correct universal answer to what brake pads to run.
Vesrah RJL's are awesome pads to run, that's all I've used this year to win the national championship for V8 HWT on my ZX10.