A boost-triggered Coolingmist system has been ordered. At first it will see duty only as insurance at high boost levels. Later on, I can see myself adding bits to make it a more integral part of my engine. The R32 washer fluid tank holds more than 4 liters - plenty big enough. But the main thing is my suspicion that Korean hi-test isn't always a steady and solid 100RON, but rather good batches and bad batches get sold and you never know what you get. Man, I wish they had pocket test kits to check "purity", like what drug dealers kingpins use to test out their product. Imagine dipping your finger into the premium petrol and then rubbing it against your gums, then saying, "mmm, seems about right, fill'er up". Ok, I'm wandering now...
I don't really see a downside to water injection, other than having to learn how to use it. As a neophyte, I'm planning to use 50/50 ethanol and water until spring, where I'll go to 100% water. From my limited perusal of water injection forums, some say windscreen fluid is a-ok, some say it's crap. Can't say I imagine blue coloring can be good for the combustion chamber, who knows what kind of residue that'll leave after being lit up at 800 degrees? It'll cost $10-$15 to fill the tank with ethanol and distilled water from the pharmacy - more than the $3 of windshield wash fluid but probably worth the peace of mind and reduce the chance of clogging the injector nozzle.
No real sacrifice of the windscreen wiper system - I'm so anal about the glass that I'll pull over and handwide the screen clean rather than have washer fluid spray willy-nilly all over my car.
AFAIK methanol will burn as part of the air-fuel mixture, so you'll have to map for it, although the stuff does have an octane of like 118 or so.
I'm thinking of installing the injector immediately after the intercooler.