Flatsides on a ZX9R

I was wondering if a set of 39mm Keihin flatsides off a ZXR750M would fit a '98 ZX9R. If so, would they be able to provide enough fuel & air (even with rejetting) given that the standard carbs are 40mm CV and would they be worth the effort?

Yep, they will work just fine with a re-jet. In fact, they are likely to flow a shitload more than the CV carbs anyway....