Is your supercharger set up going to be drawthrough or blowthrough?
I fitted a wet fogger to my supercharged A15, but I never got around to actually pulling the trigger on it. Then I puled the engine out to do a repair, and never got around to refitting the kit.
If you're running a drawtrhough set up, mount the fogger between the carb and the blower. Then you'll be able to harness the cooling of the liquid nitrous boiling into a gas, which will give you a nice spike in charge density. And a power increase greater than the power of your shot.