Since the KOWAL Hayabusa Octopus Octagonal Restrictor Plate debuted at FA, a number of players owning the silent Hayabusa model joystick asked if the unique plate was compatible. Unfortunately the Octopus was not designed for the newer model Hayabusa, as Hori took a significantly different approach to its construction. This did not stop some dedicated players from trying to develop a workaround. Of them is Twitter's @R0bbit. He offers a straightforward way to get the Hayabusa Octopus onto Hori silent model joystick.
(Please note that this mod will void the Hori fightstick warranty. We take no responsibility for the mod's use of a dremel or file to pare down the center of the original gate. Please mod at your own discretion.)
Remove the square gate from the bottom by gently pushing the tabs while lifting the gate off.
Using a Dremel (or whatever you can use), grind down the center so it's flush with the rest of the plate.
Line up the holes on the Kowal gate with the holes on the Hori gate and screw it in.
I used screws from the bottom of my Hori RAP4 Silent case. Worked perfect.
Clip the assembled gates back on the stick and have fun.
Special thanks again to @R0bbit for suggesting this workaround.