Do you know what cfm rating of fan is? Also, are all of your passive vents around bottom of tent open?
As far as your growing style, you wouldn’t really need to fill a tent from wall to wall with light. I think one of the fixtures designed to do a 4x4 would plenty. That would require you to mostly keep the plants together though in the middle of the room. Your best light will be there, as opposed to at the edges where that slightly bigger tent would probably be quite a bit weaker. Is that a problem? And don’t sweat wanting to veg and flower with the sane light. You just pick a middle of the road color mix.
An alternative would be to go with 2 long and narrow fixtures. They would probably be a little cheaper individually, but overall cost would maybe be a little higher. But them you could essentially treat it like two 2x4 areas within the same area. Would give you more freedom with spacing. I’d probably go with the one fixture, but that’s just me. We want it best for your application.
I really like to recommend the Pacific light concepts plc-6 for a 4x4. It’s not the best light, more like best bang for your buck. Problem is they’re currently out of stock. But if you have time, go and check them out. There is independent test data, and actual ppfd numbers to compare. In my opinion, it’s the cheapest real world 1000w hid replacement. Comparing par data, efficacy, and cost. Drawing 600 watts at $800, it will alleviate some of your heat issues and energy cost without giving up yield potential.
Another option is going to be the hlg 550 from horticulture lighting group. It’s normally around $1050, but they are currently running 20% off. This one uses the latest in mid power technology. Instead of having a few high powered cobs, it uses 4 pcb boards that contain 304 Samsung diodes each. This doesn’t have quite the light intensity in the middle that you’d be accustomed to, but probably more even. With 20% off, it’s one to give a good look. There’s lots of buzz about it too, so a quick Google search should give you plenty of grows to see it in action. This is probably one of the coolest running led fixtures of the size as well.
If you don’t want to spend that kind of money, you could throw a few amazon lights in there as well. But competing with the hid, it probably wouldn’t be all that much cheaper. Last I looked the viparspectra was kind of holding down the amazon light title. Two of the bigger ones will set you back $500, and I still don’t think they would be quite as good.
Timber grow lights has a few that would do the trick as well.