I think that you will need the 2ft in the veg chamber unless you can learn to train your mother plants to only grow about 8 inches high, I posted an article on it around here somewhere on Bonsai training for mothers I will try to find it, it was in the in door section I believe. If you can do that then you can take off about 6 or so inches off of your veg cab. Those fart fans can pull air in or push air out they are about as big as a bible, they are flat and do not have a big housing you mount them like a 6x9 speaker but smaller.
I think that you will have enough room with 5FT in the top, you are just going to have to know your strains. Remember when you establish a mother plant or 2 it will be allot easier because you can get much better results from a 2 or 3 ft flowered clone than a plant the same size grown from seed. A clone can have about 6 or 7 nodes and be only about 6 inches and a seedling may have only 4.
The dark room louvers are a great idea, just remember that they do restrict allot of air flow so get a bigger size than you may think will be suitable IMO.
Adieu