I just went and looked Im running the M10 nozzle. Its been a while since I have messed around with this. The nozzle is rated at 630ml/min. I have my 650s about maxed out so Im really only getting 1/4 the nozzle per cylinder.

ml/min = cc/min
.25 * 630 = 158cc per cylinder of the water/meth mixture. Since my mixture is approx. 40% meth I am really only getting 63cc of methanol and 95cc of water. If you plan on running straight water then you should probably run a nozzle less than 400ml/min.

But like I said I would run the larger nozzle and add some meth into the mix. It will let you run more timing and also let you pull some more fuel out of your injectors to lower the duty cycle. However, your setup will now rely on the meth for fuel and if you ever run out your motor will be toast if you boost it. With just water you wouldn't have this problem.