I would not mess with your effluent flow rate once set.
reducing your Co2 bubble count is a lot easier.
Unless you are using a Cole-Parmer pump.
But yeah, i'll usually try to reduce the c02. Save some pennies that way.
Raising the effluent rate a little bit might even raise your Alk. PH might be a little lower in the reactor but you are adding more of it to the tank. And the more effluent you are adding, the more chance of lowering your tank pH.
Better to reduce the C02.
Mine stays right around 8.4 dkh. Shouldn't be a problem holding it anywhere you'd like.
Lets see this dual stage. ........