This will work if you have room, but it may be more work than draining the tank and using weldon to attach "patches" to the holes. What you can do is cut two pieces of acrylic to cover the holes on both sides, some neoprene to act as a gasket between one of your patches and the original wall, and drill through the patches where the holes are in the original wall. Then use nylon thumbscrews and wing-nuts to clamp the patches on either side of the original wall. If you can get the chamber dry, or even one side dry, you can just glue your patches on with weldon. I personally don't like #16, but it will work in this case. I can;t really picture what you're talking about, so it's hard for me to know if these ideas are possibilities.