Not so good news...
Yes, it does require cutting a hole in your quarter panel which I am not willing to do SO, I went to my local junkyard and picked up two quarter panels for $100 from some explorers. I am going to use on for testing, the other for final product and store my current one in the garage in plastic, just incase I ever sell the car or get tired of the stack coming out of my car. As for H2O coming in... your car should be shut pretty tight. Nothing leaked into my MM going through that water in the picture above. Now, I don't know how well ford puts these things together, as I am rather new to the whole exploder/MM thing but my XJ is sealed tight. My XJ was known around here as AmfibiusXJ cause we would do water runs in rivers... with weights in the car, I could go under 46" without stalling! At that depth, water was being pushed UP by my wipers!
Maybe it was a Jeep thing...