I ran this set up on my supercharged golf a few years ago. was a good bang for the buck set-up and it allowed me to run a couple more pounds of boost. I eventually ended up getting rid of it though when I turbo'd my car and fixed all my knock problems with a big front mount intercooler.
Sorry, I don't know your set-up but how do you plan to quantify your results? Do you have knock detection on your car so you know if your spraying enough water/meth? When I was setting up my car I would data log the knock sensor data and timing pull. I would change the nozzle sizes, adjust boost, and advance timing till I didn't have any knock.
Your not running boost so you will be able to adjust timing, nozzel size, and when it comes on and how ard it comes on, but I was just curious what your tuning method will be?