The Strat tremolo cavity is a perfect place to mount the Clapton mid-boost circuit board if, like Eric, you never use the tremolo. Make sure the tremolo block is wedged tightly against the body with a wooden block. As for the battery, the best place is below the pickguard in the control cavity or if there is a swimming pool rout, between the pickups. I have done this many times for people who likes the booster capabilities but not taking off wood from their prized guitars.