You should be fine. Even three of the 9" diffusers would handle the output of the pump.
I am running 6 Matala 9" diffusers (three doubles) at around 9'. I will shut two lines off momentarily (for 3 or 4 seconds) to flex each double out to clean them once a month or so. One double diffuser would "almost" (8.4 cfm would be the max for 2 diffusers) handle the output from the 1023 but it would over flex the membrane and likely damage it if done continuously. So I just do it for a few seconds while watching the pressure gauge rise to balloon the membrane out to maximum flow temporarily. This should help clean off the junk that gets built up over time.
I get very good boils from six diffusers. You should get really good water boils from 4.
