You should get with tom(plantbrain). I know he usually just mists co2, using a seperate diy needlewheel pump in his sump, directed towards his return pump. Then seal off your sump and try to make it somewhat airtight. Downside is there will probably be some bubbles in the main tank.
I am OK with bubbles in the main tank to be honest. The problem now is this reactor is so big it a nightmare to try and pull out and clean. Half the time I spill water all over the floor and get annoyed with it.
Sump is already sealed so sounds like it would be rather simple, just need to figure out what equipment is needed.