Hey Tom....
I just made something similar to yours there, using another post where you went over this viewtainer. My only difference is where the Rio goes in. I have it on the side, and the viewtainer is angled at a 45 degree angle. Also, where the CO2 goes in, instead of just letting it bubble, I placed an airstone on the CO2 line on the inside of the viewtainer. That helps give an initial smaller bubble, which then gets caught in the cyclone inside the viewtainer. Works rather well. And I have no feedback going to the powerhead, and 2 relief holes in case too much CO2 gets caught up in the viewtainer, which I have not seen happen yet. I'm running near 50ppm on just over 1 bubble per second, but not quite 2. This is on a 29G.