[rotrex]

I do not expect any long term effects on the CC alloy. Exposure is very limited and the water context reduces the reactivity dramatically.
So unless you spray a lot and tend to stop your engine a fraction of a second right after a WOT run and then store it for a few months with everything on the inside being wet, ö thing will happen.

A much bigger issue is condensation. I have observed this myself in my set-up. Past a small amount of pre compressor spray, I have logged air temperature fluctuations and sudden changes in the applied ignition correction over air temperature. This can be attributed to liquid methanol / water droplets evaporating on the IAT sensor after the CC.

If you want to spray lot's for fluid through a CC, you likely need to do two things:
Increase the methanol content of the mix as methanol evaporates much faster again. Even big droplets eventually evaporate in the cylinder as any other fuel.
Second, try to generate as fine of a mist as possible, e.g. Through a air assisted nozzle.

The hotter the environment you run and the worst your CC works, the less of an issue you have with condensation. Riceracing's set-up is a nice example of a suitable combo for pre-compressor injection: toasty hot Australian weather, small factory intercooler plus high boost and flow.

Unless your setup fulfills those criteria, you are likely better off injecting post CC and/or direct port.

Smaller droplets are better. Droplets size drops with increasing fluid pump pressure for hydraulic nozzles. Properly designed jets should not show much different drop sized with their size, although the the very small ones with their small offices tend to produce the finest mist.

The more extra power you try to extract with the injection system, the more critical distribution gets. The cylinder getting the least mix will be the limiting factor.
The more methanol you inject, the less critical droplet size gets as even puddles and streams evaporate.
This is why I believe many folks get good results with more methanol.
Efficiency though smaller droplets can most of the times be compensated by more flow.