You can grow a few plants in there, but it will be a little tricky.
I have looked into that box before and it is a cool enough set up. One of the trricky things is finding a good strain that you can keep short and not too bushy. You see clones would be ideal, but seeds strech more than clones but you could still do it from seed. You would have to do some tying down of the plants when they get a little older. If you started from seed I would start off with 4 to 6 and hope for at least 3 females. If you can find some clones and get them in RockW to put into the hydro system you could try 6 at first and test the strain so to make sure it doesn't get too crowded. Look for a mostly indica strain and go to 12-12 light cycle once you get at about 7 to 8 inches. You could pull off about 4 to 5 ounces a harvest easy IMO once you got things diled in right and got over the learning curve.
Adieu