Do you already have the cool tubes? If not, I'd suggest just reconfiguring your room to start. Your filter should be up top (ceiling level) pulling the warm air from the tent, not on the floor where you currently have it. Your inlet should be near the floor on the opposite side of the filter (exhaust) and should be as big or bigger than the exhaust. If you are exhausting 10" you should have (2) 6" inlets. Do the tent walls bow in really bad when the fan is on?
Second, how warm/cool is the air you are pulling from? If the room you have the tent in is 80*F and your tent is pulling air from said room to cool the tent, your tent will never be any cooler than the room its in.....likely some degrees warmer at all times.
If you already have the cool tubes, you want a dual leg system like mentioned. The reason for this is if you have 4 lights in a row all on the same leg, the last light in that series will be a hot mess because it never sees any of the cooling air, just the hot air from the 3 lights in front of it.
If you have one fan pulling from 2 legs of 6" vented lights it wont be as restricting as pulling from a singular 4 light series on 6" line and 1 singular filter. It will also help reduce noise and cool the lights more evenly and efficiently run on 2 legs.
Quick doodle, hope this helps:
View attachment 4013347 View attachment 4013348