I got a gorilla lite on a black friday sale and it has the fewest light leaks of any tent I've seen, and I've cowered in the dark inside many of the tents listed here today. It had maybe 3 pinholes, which are easily covered by tape, but in practice, the light leaks that are going to do the serious damage come from poorly designed zippers with too little of a "flap" behind them, blocking the light that enters the tent....and also, through your vents and ducting. The one thing that gorilla does better than the tents mentioned here is blocking the light coming in from zippers-their flaps are several inches wide. If you use the 3 or so vents that most of these come with, you'll have to figure out a solution for yourself-just taping a thick piece of black carbon furnace filter over top them is "probably" enough. Even better would be to tape a box with a hole cut for the vent and another hole at the bottom of the box, so that no direct light can ever directly touch the vent. Same idea if you use the bottom ducting holes for extra ventilation-those are easier, just use a long enough run of ducting-say 4 feet, with one 90 deg turn and stick some black pantyhose at the end. The exhaust fan/ducting can be another source to check. Whatever you choose, be sure to test the hell out of your tent and make it absolutely light proof, because it isn't that hard and you only need to do it once. Turn on every light in the house, open up you window curtains, and then shut yourself inside of the tent-if it isn't pitch black, you have work to do.
