Needing advice on my setup/ventilation

I am wondering how much will my setup suffer because I have only a 4" vent to outside. The ducting could be made to be very short, less than 4 feet with only one bend. I have a 6" fan though, my carbon filter is 4" too. So I will be necking the fan down on intake and exhaust. I still am hoping I will get better performance this way than with a 4" fan which tops out at 180 or so CFM. This 6" is rated at over 400 CFM. My filter is a 4" X 18"

My setup so far: haven't grown a thing yet.
6X6X7.5 grow room/270 sq ft/90% sealed
AC/heat are ducted in if needed
Painted flat white, floor gray
2X- 400 watt MH/HPS- inline duct fan just blowing air on them.
6" inline fan-435 cfm with speed control
4"X18" 5lb/carbon filter
Ceiling mounted oscillating fan
30 pint dehumidifier just outside of growroom, near intake vent
2X-PC fans cooling the remote ballast(s)/outside of growroom

Gee, 55 views and not one reply, FUCK ALL YOU FRYBRAIN ASSHAT MUTHA FUCKERS....... and the horses you rode in on.

What is your carbon filter CFM rating?

You should be fine, the reductions you have pictured will reduce your CFM exchange but your fan should be adequate

LOL, thanks. see this post for pics and some description. https://www.icmag.com/ic/showthread.php?p=3795768#post3795768

I have decided to just go with a 6" filter to eliminate the hassle and wasted CFM's although the way this fan blows I will probably be running at a max of 1/2 speed.

I would extend your A/C duct and move it down to the lowest part of your grow room. The heat will rise and your carbon filter if sitting inside the room and exhausting out should be situated at the top of the ceiling. The way you have it now it seems that you will be sucking out nice cold air that your plants may enjoy.

The picture makes the a/c duct look closer than it is to the intake of the fan. I'm assuming you looked at the photo and not the paint drawing. I have an intake vent at floor level. When I have the fan on it is very noticable at the intake, lots of air coming in. That is what I thought was the way to do it. Intake at the bottom and exhaust from the top of the room at the opposite side, of the room.

If you have two inline fans, cool the lights with one. You'll probably need to slow down your exhaust fan if you do. Not much for it to do once you remove the heat off the lights
Fred