Will this setup work?

Im starting a personal grow and I have finished building my flowering and veg cabs and I need to figure out the best way to ventilate both areas efficiently. The way I have it setup is the veg cab is directly on top of the flowering cab. I wanted to know if would be possible to ventilate both areas with one fan. For now I'll be using one 600w HPS + air cooled hood for flowering and a 6' t5 for veg & clones. Im going to have a passive intake on the bottom of the flowering cab and the duct will be connected from the flowering cab going into the veg cab with a Y so the hot air from both cabs will be pushed into the attic. But im having a hard time figuring out if this setup would work, If I used a 6" inline fan and put it at the top of veg cab would that be enough to exhaust both grow rooms? The flowering cab is 76 cubic feet and the veg cab is 17 cubic feet.

It depends on what the cfm rating is for the fan, but if you set the Y up so that it pulls the air out of both cabinets it should work, however you are going to need to restrict the amount of air that it pulls out of the veg cabinet. This is for 2 reasons: 1 is that being you are using the t5's in the veg cabinet they don't really throw off any heat at all and it will drop the temp too low and restrict the plant development. 2 is, seeing that you are pulling all your air in through your carbon filter, if you don't restrict the amount of air it it is taking out of the veg cabinet, you wont have enough draw on the system to remove enough air from your flowering area. Here is a link to help figure out what your min requirements will be then you can guestimate how much more you will need due to having to pull air in through the filter. Hope that helps you out man.

I think the 6" will work fine as said above^^^. If you put a variable restriction on the veg intake you would be able to control the flow from that portion of the cab. You may also need a speed controller on the fan to get the temps dialed in.

I can see how that would be a problem. I plan on getting a speed controller so if I have the fan at the top of the veg cabinet and restrict some airflow then it should work? What if I used a 4" carbon filter with a 6"-4" adapter on the Y? and what's the minimum cfm I should get for both cabs? thanks for the advice, I didnt get the link btw.

http://cheaphydroponics.com/Merchant2/cfmcalc.htm this is the link for the cfm calculator, and if you knock down the size of your filter you should be fine. your best bet would be at least 150 to 175 cfm.