Yep, that does sound crazy. Lol
Unless you plan on keeping a pretty light stock, you will need more than one FX6. If you want to stock it heavily, I strongly recommend you get three of them.
Or, you could just do a little research and stick with the sump, or a combo of the sump and the FX6. The sump is more work to setup, but it is FAR easier to take care of. I have a 55 gallon sump for my 220 and it works fantastic. I wouldn’t even think of going with canisters or HOB’sover my sump. I can change the mechanical floss in just a few minutes, and the longest part of that is cutting the new piece off of the roll. Then, the course sponges can be rinsed in less than ten minutes. Remember this when you are spending two hours cleaning out your canisters. Lol.
In all seriousness, the FX6 is a good filter and will do well with a lightly stocked tank. I would recommend you leave the weirs where they are, and if you’re not going to use the bulkheads to attach to your canister(s), then just plug them up with some PVC plugs. However, if you don’t mind the plumbing, I would recommend using at least one of the bulkheads to plumb to the intake of the FX6. You can use both sides if you get another FX6.
Good luck and let us know how it goes!