Square Peg

Now I'm thinking I'll get a 6" Growbrite with the filter (HTG). Can I vent to the outside through a 4" flange/hole or will I suck the world out backwards and have to start all over? Will the fan/filter (424CFM) suffice to both clean and cool my 76cubics? Thanks.

76 cubic feet with a 424 cfm fan? You'll be alright. Might want to invest on a fan controller though, you might find that fan to be a tad strong for that space. Plus the controller will help to reduce the noise coming from the fan if that's an issue for you.

If anyone's interested, got a 4" eco plus and a can fan 2600. My guys haven't grown into smellies yet, so I don't know how it'll do in that regard, but the temp. stays at 81.5. Humidity's a bit low--35%; so it goes. Happy days.