Inline fan / carbon filter cfm question.

So i have 4 vented hoods (double ended hoods for two ligihts a piece) running 6k for flower 4k veg. Just for some insight.

I have a 10" inline fan 1100 cfm, ducting out of the room (on top of room not inside) and also cooling the lights.
I hooked my carbon filter up and its ducting out the final hood, which is about 20ft of duct from the fan up top. Its definately not sucking that strong.
The carbon filter is 8 inch rated for 935 cfm. Would a 730 cfm fan be fine to throw on the end of the carbon filter if ive already got a little pull coming from the fan up top?
I can put a 935 cfm fan in no problem i just dont want it to be sucking to strong with the added cfm from up top.

Setup.
Fan>light>light>light>light> filter

Any insight would be great.

Where is the fresh air coming from? Are you venting outside from inside?

Fresh air coming from a different fan outside... and yes venting outsidr from inside. Fan on ceiling pulls through the hoods and outside

Fresh air from outside the room or outside of the house? Assuming it's from in the house, you might have to add some make up air from the great outdoors. Otherwise it's sort of like putting your hand over a vacuum, not enough air going in and it's choking the fan. Most houses have trouble drawing air to feed exhaust systems of more than a few hundred cfm. Without any sort of makeup air system, you're still drawing air into the house to feed the exhaust, just through leaky windows/doors, cracks in the wall, etc and it's seldom enough to maintain desired flow.

No its a fan hooked up to the great outdoors! Haha
Still looking for an answer to original question tho. I bought 770 cfm. A little under the rating for the carbon fter but did some research and most say its better to be under than over.

In that case a booster fan wouldn't hurt, you're correct that it's wise to stay within the filters rated cfm though. I'd say go for it and see if you can measure any difference in cooling.

The 935 is the maximum airflow it can scrub and be effective not the minimum.
You don't have to worry about under driving them in fact they will last longer with less airflow.
Speed controller are often used with Carbon scrubbers so the temperature or noise can be controlled.