New Grow! 5x5, 2 HLG 350r, 8 plants

This will be my first attempt with this setup and hopefully all goes well! AC Infinity 5x5, AC Infinity 6” in-line duct and filter, AC Infinity controller, 2 HLG 350r, will have 8 plants of Stickey Dickie Auto, 6 in 5 gallon pots and 2 in an Earthbox (sip). Will be adding fans for circulation. Currently I have the 6” filtering to the outside for smell and to remove some unwanted temperature and humidity. I have another 4” AC Infinity in-line fan and filter! I was debating on using it to run on the outside to push more fresh air into the tent or pull air from the top of the tent and run it back down to the bottom to also give it more circulation. I was curious what all of your thoughts were on anything. I have learned with the HLG 350r do not run it at turned up at all for awhile or maybe I had it to close or too am far away!

I'd pull the slack out of that ducting to make it as least bendy as it can be.

As for 4" , likely make any difference, could impeded your extraction if its the only intake , as in if your closing off passive vents.

Try it both ways see if you notice a difference.

You may find that the 4" pairs really well with the 6". I have two 6's and had to damp-down the flow on the intake 6 since it didn't have a filter or as much ducting as my exhaust and was causing too much positive pressure in my tent. If you have the newest Controller 69 you might run them on slightly different programs and notch back the intake by a number or two.

Looking good dude.

as others said; less bends in the ducting the better it performs.

with a 6” extraction fan you can either run it passive - with vents opened up. You will need double the passive intake vents to your outtake. So 12” of passive intake for a 6” exhaust fan.
or
You can run it “active” with the 4” intake fan paired with the 6” outtake fan. You will need to dial it in to get a good exchange rate of air.

I personally wouldn’t run a charcoal filter until I was in flowering. I don’t want to be replacing them frequently.