Just read Nebula's tutorial on using a blackout tent to get 2 harvests per summer. I've done something very much like this the last 3 summers, but for privacy not a second crop. So NO tall plants. My system: 1) I use a modified Screen of Green technique, pinning down each main branch with stakes to produce short, wide plants, then 2) I cover them with sheets of black plastic each evening after 12 or 13 hours of light, and remove them at dark. About the end of week # 1 I pinch off the long end growing tips and allow everything to grow freely. Plants stay about 25 inches tall. Security is improved by planting tall vegetables between the pot plants and my neighbor's yard. Harvests are smaller than with full sized plants, but still decent, and the quality is great because of all that mid-summer sun.