You will probably lose quite a bit of CO2 if your spray bar is 1 inch above the water surface and the water is splashing down.
Can you set the spray bar so that it is just at water level? That way, the water from the filter return is gently rippling the surface of the water; this is the ideal amount of surface agitation you want to have to prevent excessive CO2 off gas (diffusion).
Not trying to hijack, but I've been running a hagen mini just under the filter intake. The tiny little bubbles get sucked up and shot out through the spray bar below the surface (about 2"), creating gentle agitation. Still, I don't have good co2 concentration with at least 6 bps. If this isn't germane I'll start another thread.