I too have struggled with this. I did find a 6 inch clip fan at Big Lots that actually clips to the tent pole. It doesn't oscillate though unfortunately. I actually have an extra of those dual window fans that I may throw in as well since others like them. I have a humidifier (ultrasonic cool mist) on the outside of the tent on the floor by the passive intake. My fan keeps an excellent negative air pressure so the mist is pulled right in and keeps my humidity around 45-55% during veg. Will the moisture be too much for that window fan if I fix the fan right on the inside of the passive vent? I could put it on the other side, but that would interrupt the flow of air to my exhaust as the exhaust is top left and the intake is bottom right. The clip fan is already right above the passive intake blowing up at the canopy and toward the light and therefore toward the exhaust.