me and my buddy built this box starting off with 2 rubbermaid tubs
1. fasten the light fixture on the top tub, either by screwing fixture to top or by cutting out 4 holes in the tub so your lights can poke through and leaving the entire fixture outside on top of the box.
2.cut an intake hole and install a duct facing downward. then cut an exhaust hole, install a computer type fan in duct then we stuffed the rest of the duct with carbon air filter so it filtered the exiting air.
3. line entire inside of the top and bottom with mylar, we used a combo of mylar we had and emrgency blankets bought at wally world for 1.99. there also mylar.
4.then we bought 6 pots, well actually small trash cans and cut holes in the bottom for airation and water exit.
5. we put telephone books and boxes underneath the pots to raise them up to lights. when you have no more option for growth you have to build a spacer, i did this by buying another rubbermaid tub and cutting the bottom off it making it a nice spacer. then we tapped that to thetop of the bottom tub raising the height about bouble. worked great
any questions get back...
we pulled about 5 ounces of c-99 out of this little box
light fixture used in box( i also used it in a closet grow i did as seen in this picture)