Mine spins off (threaded pipe) but I like the ramp with flap style better than mine.
One thing to note, the more "whip" you cause the more mud that'll sling depending on the speed you are running the line at.
My boat and Dipper/mate can get fairly muddy due to just having a U shaped pipe.
If you are ever on Kent Island, go to western auto. They have the scoops made from stainless (probably like the ramp you referred to). You can attach a rubber flap. These are much like what a lot of commercial crabbers are using. I think I have some left over rubber from when I did my flap, if anyone needs some.