I've done a lot of methanol injection work, but always turbos and never a supercharger, so my advice may be useless.
If you spill methanol that stuff evaporates almost as soon as it hits the ground ... unless you're spraying an astronomical amount of methanol, i have a hard time seeing a situation where there will be enough to 1. Pool, and 2. "explode," especially seeing as how methanol is not combustive. It's flammable for sure, but it should never "blow up."
Now, as far as the injection causing damage to the rotors, that's another conversation entirely. We sprayed pre-turbo methanol + water with success, but there are several cases where the combination of high speed and large droplet size has caused pitting and damage to a turbine wheel.
I would want to spray pre-supercharger to potentially cool the supercharger itself, but i imagine that could probably cause more problems than it is worth, and just spraying after the intercooler may be best.