I've been running the dual kit for the last several year:
I've had no issues. The Amsoil Dual Bypass has a valve built in that forces a certain amount of oil through the bypass filter, the rest goes through the regular full flow. When you go to WOT or any load on the oil system, this valve closes the input to the bypass filter to prevent any back backpressure. Then all the oil flows through the full flow filter like a normal system. When you let off the gas and oil pressure returns to normal, the valve forces the oil into the bypass once again.
The fender would probably be a better mounting place, someone I know used this space in his Taurus. Since I do shows using my car as a display for my business, I decided I wanted it somewhere more noticable. The previous owner bent the radiator support under the car so I was able to use the stock 90 degree brackets that come with this kit to mount it. On a normal car, you would probably have to make a different bracket with less of an angle than the 90 degree one. But then you would probably have to figure some sort of mounting option in the fender as well. Last month I replaced the filters you see in the picture with the new Ea Oil Filter and Ea Bypass Filter Amsoil now has.