IMO and from what I have read, anything under about 150psi of pressure creating a extremely fine mist of water is next to pointless!
The key point is that the water must evaporate – it is this change of state from water to a gas which absorbs the energy/heat. If the water droplets do not evaporate, they basically provide almost no cooling performance. And the key to getting water to evaporate is to use very small drops – an atomised mist – which dramatically increases the surface-area-to-volume-ratio of each drop, promoting evaporation.
But as you say it's just for fun and keeps you from drinking beer! lol
One thing I would do differently is use a Charge temp switch not a boost preesure switch, that way you attempt to maintain a constant control over the charge temps rather than only cooling when on boost.