Sean,
I Like it. I think it will work well. You shouldn't get any bubbles especially before it is being installed right before your canister filter. I know you only showed the reactor itself, so I am not sure if you have plans to do this. I would do 2 things to make that set-up a little safer. I recommend a check valve on your CO2 line. I also think that you should put a bead of silicone (aquarium safe of course) around the threads of your CO2 brass barb fitting that you tapped. I am not sure what the material of the main tube is made of, but it's most likely a polycarbonate, which does not lend itself well to tapping, and especially for sealing threads like an NPT thread. I really do like the design. I would just take the brass fitting out, and put a bead of the silicone around the threads, and screw it back in place. This is just me, but I kow how much my fiance' would freak if we had to clean up a 110 gallon mess...lol