I actually have the top mounted restrictor, but I don't think I'll be using it. It's really nice, but I've noticed that the insert rides up just a hair when the stick is being pushed around. It's very faint, but I can hear the plastic insert moving slightly. That's really a nitpick since I probably wouldn't be able to hear it during play.
The bigger issue is that the restrictor sits proud of the CP. A dust cover would look silly on that. I could flush mount it, but then I'd need to have some way (a tool maybe) to pop the insert out.
I think a permenant solution is what I'm looking for.