I am using one with an OS 91fx.
Perry recommends using the fitting and hose provided. I figured that they tried everything else, so I went with what they said.
I used a "T" and check valve to divert excess fuel back to the tank. The "T" is between the pump and carb, as close to the carb as I could get. The check valve is between the "T" and tank and is used to allow the extra fuel to return to the tank, but prevent air from being sucked in by the carb.