Honestly there is no problem at all being that the pressure is "Negative"... It's sucking the lid down. There is absolutely No leaking from the lid at all. And honestly I think that this fact alone will help with the overall longevity of the system. The pump is sucking on the intake. Which in turn brings negative pressure to everthing else. I would say that the canister is okay as well being that they only way that the pressure would become greater is if the filter media would become so clogged that it started to implode the can because of the suction from the pump. But, once I make media trays, that will support the walls of the can. I plan on taking samller pails, sutting the bottom 3" off, creating a meash out of the bottom and slits in the sides of each of them. This will allow media in the middle and sponges on the sides. Just like the FX5.....
Technically, you could do the same thing with a large 40-50 gallon "brute" Garbage Can and have a parge Extrenal Pump hooked to it VIA a 1" - 1.5" Bulkhead with a grate covering it and then layers upon layers of filter media filling the garbage can.
Then Have some sort of lid on top. YOU could put a bulkhead in the side of the can near the top with some PVC leading to a 90* pooring over the top of the media. Would basically be a sump in can!
