DIY fan reducer

Help my fan is too strong for my 4x4x6.5 grow tent and is lowering humidity to 30%. Is there a way to hook one Side up to a bus tub cutting and exact hole and running some vent out the other side to slow it down without a dimming control? Or should I just mount it at the top and suck air out which would probably still give me a humidity problem. I already have a humidifier in the tent. Any help is good help.

Maybe try attaching a y piece to the fan and having the y piece attach to the light and a carbon filter, have ducting from the light pull in air straight from outside the tent. So the fan then has 2 jobs but one of them is using more airflow (the light) to cool it but also still keeping light temps aways from the tent by pulling outside air through? Just a random thought/idea that might or might not even work. But a speed controller would be your best bet.
Good luck man

Thank you sir, unfortunately I rushed to get a light since its now legal to grow in Oregon and got a 400 watt Howard ballast high bay HPS light that is not air cooled. I have it just sucking air out creating negative pressure temp stays around 78 80 with RH being 45 to 65. All is well except now it keeps tripping the 15 Amp breaker in my apartment with the humidifier on smh.