My (Cathar original) White Water seems to be getting along with my Iwaki 20-RZ just fine. Although the nozzle may be designed to work with low flow systems, it will work even better if you can keep the flow rate up (I've estimated my flow rate at around 7.6 lpm using some of Bill's data and the manufacturer's P-Q curve). So, yeah, I would say that an Iwaki is fine.
[Edit] How did this become a discussion about the WW again? [/Edit]